I haven't used Jamstix, but recently upgraded from EZD1 to EZD2. It's a big difference and in a good way. I'm glad I finally upgraded.
+1
Glad I upgraded.
Regarding the MIDI groove conversation: Don't forget that, instead of searching/auditioning grooves, you can simply use/edit the exported GM MIDI drum track data from an SMF you're familiar with. Instead of driving yourself crazy trying to find beats to use/edit for, say, "Soul Vaccination", why not start by auditioning the SMF version? If you're equating your beats to a song you know, it's not a bad way to go.