I have not used Z-wave extensively.... but I have used an application called HomeSeer, which now supports Z-wave for home automation. I see there are a few people trying to port homeseer to the Pi.
At one time, I had nearly 70 devices managed in my home... but it was all X10. Z-wave had just started coming out and was costly. X10 didn't scale, so I dropped interest and went on to other hobbies.
Good luck... I'll watch this thread to see if anyone else replies.