I have the BetaMonkey Drum Werks VII, and it's pretty good. I have some free samples from, I think, Drums on Demand, which also sound very good and have a very user-friendly file-naming system, but DoD's catalogue isn't (at this time) as rock-oriented as BetaMonkey and is more expensive (their best collection for rock is USD 80, while the BetaMonkey 3-pack is just USD 60 for the next couple of days .....
Mmm, damn, that's tempting. I hadn't been planning on ordering more drum loops anytime real soon, but that's really tempting. Uh, I'm gonna try to resist until at least tomorrow! :P
I sometimes do my own programming and sometimes use loops -- it depends on how I'm approaching the recording, how I feel in the moment. There's a lot of satisfaction from tweaking about the programming just the way you want, but there's equally a ot of satisfaction in just dropping in some loops and getting on with the other parts of the song! Many people who are more into the Zen of Mixing get fed up with loops because you can't twiddle with the levels and effects on the individual drums -- you've got what you've got -- but I've been coming to appreciate that, for a newbie (like me!), drum loops are a very handy way to hear how people mix drums that are meant to sit in a mix with other instruments. Handy reference points when you start struggling to mix your own programmed-from-scratch drum parts! :)