For what it's worth, I'm running 5.3 with the 4.11 opengl.dll file (as outlined in the describe your fixes threat"). Runs like a dream. Game play is fine, as are the movies. I'm not very far into the game though I only just got to Telos, so I presume if there are show stopper bugs they're all still ahead of me.
I think (since I got to Telos) the foot steps effect is starting to get a bit of a weird echoing effect going on when I run, but other than its going well.
About once a night, it crashes to the desktop when I try to load a new scene, but that's not much worse than most other windows programs, so it's tolerable as far as i'm concerned.
I've got a Radeon X300 for the record, and the 5.3 drivers made about 1000 pts differnce on 3d benchmark over whatever my HP shipped with.