I suppose us WoZ owners cannot complain
We all (should have) paid in full last year, still no pictures of finished product, nor have we played test versions, or have a definite delvery date 
Same went for BBB, and we really had to pray they would get done. At least with Stern you can be fairly confident that the product will come. WoZ is pretty much the same risk as BBB I suppose.
As for a deposit, Gav defines it perfectly "given to prove that you will honour the final transaction", it's exactly the legal definition. They are generally not refundable (despite some comments here) unless agreed.
