Some general tips for those having trouble launching / opening the game / crashing. Some people may be experiencing a black screen with a cursor showing and sound / audio still working. These suggestions work for that too, as well as lag / stuttering:
-- If you're using Windows 7, right click the game's exe -> properties -- and set the compatibility to Windows XP Service Pack 3 (SP3)
-- Run the game in administrator mode
-- Apply the latest game patch
-- Change your resolution (preferably to something lower), and then run the game
-- Verify the integrity of your game cache through Steam
-- Delete your local content, and then try downloading and re-installing
-- Though not commonly necessary for this game, you can try setting the game to run with only 1 or 2 cores by loading task manager while the game is open (CTRL+ALT+DEL), right clicking the game under the processes tab, selecting "set affinity" and then choosing the first 2 cores. This may fix some lag problems or general playability problems
-- Though not recommended, you can also try loading task manager as mentioned above, right clicking the game under the "Processes" tab, Set Priority -> High. This generally is not recommended as it can cause instability with the game that can cause your game to freeze. It does not solve a problem if it creates another one, now does it? That's why I won't recommend it