Jamstix is one of those things where you have to read the manual, be thoroughly confused, play around with it a bit, go back to the manual, experience a couple of "aha!" moments, play with it again, and then go back to the manual with a new found confidence that you know what in the hell it's talking about. As soon as the Jamstix workflow clicks, the only remaining problem is in trying to understand the esoteric drumming terminology that's used in The Brain. But that's largely a matter of experimentation and tweaking things semi-randomly until you get the results you want.
I love Jamstix and unlike most users I think, I use it for electronic styles of music. It's the best way I've found of humanizing what would otherwise be static, quantized MIDI. You can give it a MIDI file and say here, have one of your drummers play with that basic pattern. The results are often amazing.
I never used the included drum kits. I've always used it as a MIDI generator - I connect the MIDI output to things like Battery, Geist, Addictive Drums and whatever drum VST's I have. You just have to make sure your buffer is not too high (for me, 512 or lower) because Sonar seems to have trouble with MIDI output timing past a certain buffer size. I've even connected it to synths, and tuned the MIDI note of each drum to a note in a scale. You can get some amazingly unique synth parts like that, even bass lines if you tweak it right.
I really hope Jamstix 4 is all it's cracked up to be. I had the experience of waiting a similar length of time for Geist 2 and it turned out to be a complete turkey for me. I'm a little worried about that whole 3D drum kit though. It seems a little unnecessary and waste of processing power (also a waste of development time that could have been spent refining the other parts of the program). But we will see.