I wanted to like it because of the story and all but I thought the Xbox version was an unoptimized, stuttering, jerky, bad frame-rate pile of poo. If they fix all of that stuff in the pc version I might try it again when under $20.
According to the reviews I have seen the have fixed the frame rate problems, but the textures are still lacking. From IGN:
Gamers who were originally interested in the Xbox release of Advent Rising will immediately want to know if the frame rate issues persist on the PC. Thankfully, the game now runs smoothly without slowdown even on a densely populated battlefield. My Radeon 9800 pro easily pushed the game along at even the higher settings. Effects like the way space is warped around Gideon's surge attack and the fiery sparks of explosions are impressive visual additions. However, due to the increased capability and higher expectations on the PC, this doesn't automatically bump up our rating of the graphics. The visuals are decent but never stunning and in some areas feel dated. Also, the game possesses texture work that is bland on a television and even duller on the higher resolution of a monitor.