I found some of the settings from
this site helped with performance a lot particularly the file optimisations for the Engine.ini and GameUserSettings.ini. The launch options to use shader model 4 and d3d10 made the graphics look pretty bad so I just used the -USEALLAVAILABLECORES switch but I'm not sure if that made any difference. With my 780Ti I went from ~18 FPS when I first launched the game to being able to average ~60 FPS with most of the settings turned up at 1440p.
The main bug that ruins it for me (I'm only interested in single player) is the way the dinos get stuck in the scenery. I'll be trying to explore the island with my tamed dinos following, turn round and find they're no longer with me. I'll have to backtrack until I find them and chop down whatever tree that's spawned through their body hoping that I don't kill the dino in the process. This makes exploring so painful that I just gave up.
The excuse from the developers seems to be that whilst the game is in Alpha the focus is on content development and that bug fixes will be implemented once the game goes to Beta. What concerns me about what could be a brilliant game is that it is supposed to be released as a finished product in June and they still apparently have not got to the bug fixing stage.