[quote name='maingon']its not separate, Batman AA and Fallout 3 for pc show up on my xbox 360 achievement points[/QUOTE]
Maingon is correct; back when GFWL first came out, there was a big fuss made about the PC version of Gears of War's gamerscore being completely separate from the 360's version. So, if you owned both and got maximum points in each, yes, you'd end up with 2000 gamerscore total for doing the same things on both platforms.
In all honesty, though, no one should care enough about their gamerscore enough to whine about it either way (not saying that anyone here is). It's just an arbitrary system designed to give you more to earn (and, thus, reason to play) in each title than simply completing it, and, regardless of how high your score is, it impresses no one.
Sorry for the rant, and thanks, OP, for the heads-up! I've been looking for a deal on this after I failed to pick it up during the Christmas Steam sale. Here's hoping it runs great on my machine!