The first 2 Gears of War reviews are by people who have never played it on PC. That being said, you can ignore their reviews. If you have a good PC with a video card better than a GeForce 7900, you should be able to play it, although not at that great of settings. But really, if you're a FPS player, get an 8800 or the equivalent. The multiplayer mode is pretty important because some enemies require teamwork or luck on higher difficulties, so Internet and a WindowsLive (which is free) is pretty important.
As for gameplay, it's the best (and possibly first) shooter so far to use cover as a part of combat. Seems like ducking for cover while your enemy rains down a torrent of bullets should have been an important part of shooters sooner. The strategies such as flanking and cover really come into play to make it seem more like a real gunfight than any other game I've played. As an amazing added bonus, the standard pistol whip has been replaced with a gun with a chainsaw on the end. If you want to see what kind of gore can be pulled off with modern graphics and an "M" rating, you should play this game. This is the most fun I've had in a shooter since Goldeneye.