I've been a Bronica fan for years and years and still use an ETR as a daily shooter. I have a very nice "S" but don't use it often because I fear it may fail someday and I won't be able to find a replacement.
Has anybody seen a Z, D, or S for sale?
I have seen a D for sale only once on eBay, so it must be relatively rare. The S is much common. If you want a user camera, I would recommend a S2A. They are more reliable than the earlier cameras.
I'm primarily a collector that actually uses his cameras. I already have an "S" and love it dearly. I don't mind the S2 but I'm always looking to get my hands on a Z, D, or S. Here in the States at least they are rare as hens teeth. I'll even buy a broken one at this point.