I've been watching and occasionally commenting on all this Behringer clone discussion across the web and it wasn't until this thread someone mentioning that the UBXA won't become a 'classic' the way the original did that I remembered the Realistic Concertmate MG1. Those still show up on the 2nd market every so often and still command a rather high price for a Realistic synth. Admittedly it's not a clone of any Moog in particular, but it's interesting to see Peter Gabriel on the list of users considering he was also a Fairlight owner. I've heard one in real life and they kicked arse for what they were.
Realistic did heaps of 'clones' of Casiotones in the 80's, albeit with the blessings of Casio. In that way there is a little bit of a difference there to what Behringer is doing now, but those Casiotones they reproduced were pretty much beginners keyboards and are hardly 80's classics now (if indeed they are still running). That said, I really do miss my old Realistic sampling keyboard and still curse that person who poured water over it to stop her kids annoy her with it (you could have just taken the batteries out!).
Another consideration is, if they are all circuitry and the are going to be (relatively) cheap, there will most definitely be mods being propose for it from day one. Interesting times.