I've been toying with the idea of buying Geist recently. It's quite expensive but really seems amazing in terms of drum sequencing. Sonar doesn't quite cut it in the drum programming dept. It's OK but I find it quite clumsy and awkward to get drum ideas down quickly, and as for real time groove tweaking forget about it. Geist seems like the best of both worlds, a drum machine and "DAW" in one.
Some time ago I bought the Driven Machine Drums Strikes Back library of vintage analog drum hits, and they are superb. They hardly need any tweaking at all and it's so easy to get a great sounding kit out of them. I've been loading them into Battery - it's just a shame that program doesn't have a built in sequencer too. Downloaded the demo of Geist and am going to play with it tonight. Might well try this too.