You can bypass GFWL by downloading xliveless. It will also bypass the need for Rockstar Social Club.
The controls are more oriented for a controller. The aim assist is horrible in every GTA game. If anything; use a controller for movement and driving and switch to a mouse for shooting. The KB controls aren't horrible but definitely not optimal for the sluggish movement.
Bugs are really minor. There's some z-fighting here and there. Textures load slow if you push your settings higher than what you can handle. Your character can get locked trying to get into a vehicle and unable to cancel until you've started the hijack. Just minor stuff that are rare occurrences or can be fixed by the user.
Thanks guys for the responses! Picked it up with that Rockstar deal on Steam and haven't had as much trouble with it as I thought I would. Sounds like I really need a controller to go with this though because I cannot play this with a keyboard and mouse.
The biggest thing I would really like when using KBM is an "auto-walk" key. Just press a key and you start walking (modifiable by using the sprint trigger). Walking is slow enough as it is, the RSI really starts kicking in if you need to walk a long distance.