Alright, just played the first 3 levels on PC via Steam.
First impression : UBI Login system didn't recognize my UBI.com username and password, had to trigger a password reset to be able to log in.
GTX 470 (and 480) are both detected as not supported cards, so each time you start up the game you get another prompt that asks you if you want to continue.
Mouse movement is a bit weird, slightly laggy. Had to turn up mouse sensitivity for it to feel normal-ish again. That being said, having mouseaim AND Mark and Execute makes an already easy game even easier.
Default controls look like this :
WASD movement
R - Reload
F - gadget
C - close quarters combat/body shield
Q - Mark
E - Execute
Shift - run toggle
Control - Crouch Toggle.
Item select - mouse wheel
Left Mouse button to shoot, Right Mouse button to get into cover, Middle Mouse button to zoom in.
Game looks great at 2540x1440. Don't have fraps or anything running at the moment but the framerate feels like it stays above 30 most of the time with vsync on.
Controls are okay, but for some reason they took out the best thing about previous Splinter Cell games on PC - the mouse run.
Running on PC is a toggle now, triggered by the shift button (which isn't anywhere near as good as using the mouse wheel to determine run speed).
Looking back, precision movement control probably isn't needed in a game like this, though something about the toggle just doesn't feel right (I'd rather use a hold to run).