I said I was done with this thread and normally I'd stick to my word but since I was asked a question...
FP-100B has indeed been discontinued but since no one but me apparently uses the stuff, Fujifilm USA has written that they are worried that they won't be able to sell off the stock before it all expires at the end of the year. The stuff works fine past the overly conservative expiry date (I think analog manufacturers have shot themselves in the foot partly because of their expiry dates but that is for another rant than this one...).
I find real live people find instant pictures are fun for proofing but I have not shot real supermodels who might find waiting 30s annoying. Perhaps if I'm shooting a real pro model they would laugh me out of the studio for taking fuji instant proofs. I don't know.
People who get paid to model usually don't bother. More like brides and grooms, relatives, kids and what not. And if we're talking fp-100C which is the one available, as mentioned, it would be a lot more than 30s..