Yeah, I was insanely pleased with the co-op ness of the Gears series as well (since I don't own an Xbox ^^), and had no idea that you could play multiplayer vs bots as WELL, that spices things up!
Although, I think the main story drifted slightly from the sense of co-operation often splitting up the paths of Dom and Marcus, a lot more than Gears 1 did anyway.
The bots are a lifesaver for me and my friends, as well. Something about kids screaming in my ear just put me off online, although me sucking was a bigger part of it.
Man, the Horde mode is all the fun of playing a single-player game with your friends, without having to kinda hope they die so you can get the controller back.