I've been playing Darkfall for a while now. Its definitely the "Demon's Souls" of MMOs, extremely unforgiving, the world is ruthless and cutthroat. The ingame community is very cool, but its normally that way when a game has a niche subscriber base. That doesn't mean they won't kill you without hesitation though but they'll probably strike up a conversation after dry looting your corpse =)
There are a few things I think hold Darkfall back from Sandbox greatness. Most importantly, there just aren't enough toys to play with. The most fully fleshed out features in the game are catered pretty much completely towards PvP (clan warfare/sieges/naval combat/politics/alliances), very little caters towards just social interaction (think UO). Second, is the game is very VERY grindy to say the least, I don't believe I have ever played a game where it was so incredibly slow to noticeably raise your skills and its a very common complaint on the game's boards.
If you can overlook that , have the stomach and patience for easily the most ruthless game on the market, Darkfall will probably grow on you fast. I could go into vast detail if you want me to, but its probably worth trying out anyway. As you said, some people love the game, others hate it.