Oh, hold on, I didnt realise you were talking about an ASIC appliance.
EDIT: or FPGA or whatever it is.
There's a lot changing at the moment, from what I can see. BFL is about to release some new devices, although some people seem to think that they never will get them released. But if they do, then it changes everything.
EDIT: ok, first lesson: research before post. Anyway, nice discussion here
http://www.reddit.com/r/Bitcoin/comments/1a0hnn/would_it_be_worth_it_to_buy_a_bitforce_jalapeno/