So i had about 2 hours with the beta before the server went down, my thoughts.
The beta download is about 3GB, and about 500MB patch. Pretty small. The game also patch itself while you are playing.
Initially, the graphics wasn't looking that great, especially if you're coming from TERA or GW2. It's certainly not bad, the landscapes looks just quite good (see screenshots) , the character models definitely are not as vivid and "crisp" as GW2s . I am however feeling this game is running much smoother than GW2, i am playing it on max settings, so the lower graphical detail might help with low end PCs.
Now that said, the customization options in terms of looks are at least very varied. All the classic sliders are back, you know, breast size, waist to hip ratio , arm/leg/feet length and width and so on. There's even a slider for "nail length". So within your racial limits, you tweak a few things, but unfortunately you can't turn your Human into a Dwarf with the sliders. If you want to play a short character, you need to pick the correct race etc.
So far there's a bunch of races, Human,Elf,Half-Elf, Half-Orc, Tiefling, Halfling, Dwarf and more with a "coming soon" sign..i imagine they are hiding Drow for last.
Rolling up a character is classic DnD, you pick your class (only 4 atm) , Trickster Rogue, Devoted Cleric, Control Wizard, Guardian Fighter . I'm a bit vague with DnD classes at this stage so i'm not sure if the naming convention implies there can be other types of Rogues,Clerics,Wizards and Fighters as starter classes and whether you pick another "path" later on on the existing options.
From there you do the random dice rolling thing, which you can repeat until you get your primary stat where you want. You pick a deity , an origin story and off you go.
Initially you do what looks like a tutorial, but it's in an open world area (there's other players too). You'll do the odd quest and basically be routed towards the big city. The starter city , which is clearly an open world hub for everything, is a good size. I did not feel i need portals to travel around the city, something GW2/Tera/Aion was overcompensating with having these mega cities that can be a pain to navigate imho.

(View from the starter area towards the city, the floating island is also accessible via a portal)
Running around the town, all the usual things are there, bank, guild, mail , auction house, merchants, mount merchant etc. There's also the the job "board" which opens up the Foundry created content list.
My initial quest sent me into my first solo instance. It kinda works like Dragon Age, you walk out of the city gate and a world map will show. On the map will be markers you can teleport to based on your quest. So it's definitely similar to DDO / Guildwars 1 with the instances. Some "entrances" are in the town, some are outside etc.
Combat:
It's definitely action combat. It's not as slow as TERA, but work the same. You got a targeting reticule, you point your mouse in the direction of the mob and fire off abilities. You can press "Alt" and go into "investigation mode" which basically just gives you a mouse pointer so you can click on things (again, same as TERA).
If you are using an ability that explicitly needs a target, the ability won't fire unless the reticule is actually on a mob (reticule change red when on an enemy etc). Left and Right click have by default 2 abilities linked to it. There's a "dodge" ability linked to the "Shift" key and is based on your class, fighters will block, thieves will do their tumble, clerics do some sort of "slide" etc. To dodge you need action points, so you can't do it indefinitely, but on my cleric i could dodge 2.5 times before running out of action points (which regens quite fast). Dodging is not a "cooldown" ability, if you got the action points you can do it. I definitely enjoyed this dodge mechanism alot more than GW2s, it feels like something you -want- to do all the time and not a situational "once per fight" thing like in Secret World/GW2.
I rolled a Cleric on purpose to see what the healer class would be like, and i am so far pleasantly surprised. It's not slow, the "slide" dodge is impressive enough that i use it all the time. In other words, my Cleric is not standing still and spamming an ability while mobs are clobbering her. I started off with a spear throw magical ability (left click), which is kind like a instant cast damage spell and a type of DOT on the right click. The DOT will heal me (and everyone else) everytime i hit the enemy. So immediately the mechanic is obvious here. Up to lvl 6, i have yet to actually "heal self" directly.
The animations are nice and smooth, the jumping animation looks solid. (if you came from Secret World or LOTRO you'll know how bad jumping animations can be).
Overall, i'd say combat is leaning towards a Diablo-esque feeling (you will be clicking alot) , but with a bit more of a close up dodging affair. Enemies will do the "pre-warning" thing with a circle/shape on the ground (same as in GW2) and then you need to move.
Character Leveling/Building:
Up to level 6 , not much happened here. I automatically gained my powers (no trainer or selection). There's a few power "trees" which seem to be situational. So you get your "At Will" tree, which is the powers you can do anytime, anywhere (usually the ones on your mouse buttons). There is a "Class" tree, with class specific powers (not sure how this differs from the At-Will) , also a "General" tree with your racials and so on.
Then there is the "Daily" tree, this is abilities that seem to be based on a little square thingy on your HUD that fills up. I'm not sure if it's actually just a timer or whether something else fills it up faster (i.e. being in combat) , needless to say, it fills up, once it is full you can use one of your "Daily" abilities which are something much bigger than your usual abilities. In my Cleric's case it's an angel coming down and slamming the mob to the ground for alot of damage. Even though the tree says "Daily" it's certainly not a real "day" , i could use this multiple times in a dungeon run.
The last tree is the "Encounter" ability tree. I'm not quite sure how it differs from "At Will" abilities, but i suppose it only works in dungeons? So my first AOE is an encounter ability and well, it's instant cast, 5 second cooldown and i could use it all the time (in combat).
These trees don't leave you much choice as far as i can tell, you get an ability at lvl x and it unlocks and so on. I didn't see a split in these trees yet.
Now the customisation seems to come under the "Feats" part. There you can definitely choose a path and specialise. Kinda like becoming a different "type" of Cleric. On my Cleric i spotted 4 paths. I'm not quite sure if you get actual abilities here , but the first few blocks seem to primarily improve specific abilities or related stats. Example is on the healing path there is one can turn a single target power into a multi target power etc.
It doesn't seem too complex, like Rift. You most likely won't be switching roles on the fly either (or rather i didn't see a "make a new build" feature). I got no idea how flexible the feats are in terms of setting/resetting. That said, it does seem more interesting than GW2, where i wasn't seeing character progression past lvl 40 in terms of powers.
The content:
So here i think is where the make or break is going to happen. The combat,classes,graphics,ui and all that is imho all pretty solid, i really can't complain about it.
The initial quests were all typical MMO affair, fetch this, kill 10 rats etc. The combat being actiony is certainly making up for quests being nothing new. The main NPCs are all voiced, and a nice feature, you can continue listening to them after you already left and accepted the quest. I feel the NPC interaction is better than GW2, in terms of how the dialogs look and work. The actual quests and what they say is still debatable whether people are going to read it, so far i didn't feel the quests or story was any more or less interesting than standard MMO.
However, i immediately made a bee line for the Foundry content . Seems there's already a whole bunch of things created by enthusiastic users. So i figured i'll see what this will feel like. I picked an adventure on the list which seemed to have a good rating and went to a NPC in town to get instruction . You can immediately see someone else wrote the quest text and dialog text , the style being different. The particular author being more of a story writer or dungeon master writer. So ironically i was prone to read the text more. I jumped into the instance , which was in a forest. I can see users can do alot of interesting things if they want. They do NOT have to do alot of combat even! I see the foundry rate the user content in terms of length and how much combat is in there.
Anyway, when i first entered this forest, there were things laying around a campfire and i could "interact" with these items to get a description of what might be going on. So a few combat sequences followed, and then some more things to investigate and so on.
It did feel like a DDO instance, but with a totally unpredictable story and direction.
I think the Foundry will be brilliant in a group and even solo , granted enough users create content and be good at it. This particular adventure, i do not know how much was "template" and how much was custom made, but i certainly did not feel it was low quality.
For a FREE Game, i definitely like it, it feels quite polished in beta.

(This is how your character looks in the game up close and in the in-game sequences)

(This is the foundry interface, with some user content already)

(In town, with other players, looks typical MMO).