^ Glad to, the Roland pup is bass specific. This is the older model, GK2B. The newer model GK3B is a bit more compact and supposedly tracks a bit better, although having owned both, I could tell very little difference in their tracking. The pup will cover from 4 to 6 strings, so I opted to leave the B string out. Latency gets worse with these pups the lower you go on the neck. With a proper setup, they do a fairly respectable job of keeping latency down though.
Cool sounds abound, depending on what your synth module is. I'm using a GR-20 with mine, compact, easy to use, but not very tweakable. I'm running the GR-20 into the fx return on the FET channel on my GB 12.0 and then mixing the two signals to taste. Most often, I'm using either string patches, fretless bass, some bass synth stuff. Things along those lines.
With the 7 string, I've started doing some chordal work using a Fender Rhodes sound,....verrrrrry cool, and gets a great "how'd he do that?" response from the crowd. Another fun one is doing a cover of Morphines "You look like Rain" I loop the bass/organ line, then play a sax patch on top of that, and sing the tune. Big fun on a big bass.
If you'd like any more info, PM me and will be glad to share what limited knowledge I have on them.