I'm a guitarist who knows little about programming drums. My interests are straight forward rock and pop. When getting started in PC recording about a year ago, I tried a few different things (Battery, DR-008, Jamstix, Slicy Drummer) but ended up getting Groove Agent. I really like it! For getting a basic song constructed, intro, verses, chorus, fills, bridge, etc. there is nothing that could possibly be simpler.
But with all that simplicity you, of course, get limitations. There are just not enough variations of my favorite styles and now I'm looking for something to augment Groove Agent. Everyone keeps raving about Stylus RMX, but it seems like there's not too many people using it for basic rock and pop drums. On the other hand BFD seems like way too much work to get a good result.
So I'm leaning toward getting RMX with Backbeat and maybe some other REX libraries. I'd be great to hear from others who are happy with this combination.