I also love CS:S because every FPS I've ever bought for a console has sucked. And CS:S doesn't have this constant deathmatch respawn felgercarb like every other online multiplayer fps.
Gears is such a great game the only complaint is that it's too short. Which really it's just as long as Half Life 2 in chapters and general travel and what not without all the back travel.
The system is fantastic and if it'd get a PC translation that'd be great because then they could get more creative with enemy placement. Since you do have a more true 360 x 360 degree reaction plane to deal with. The controller just can't do it sharp enough so games like Halo and Gears are designed with that in mind.