I hate to keep being Debbie Downer but I am confused as to why some of you don't seem to understand the current situation. As of right ‘now’, even  if you got the chips for free, electricity for free, SB shipped the boards for FREE, you WOULD NOT make ROI.  In fact if someone came up to me TODAY with a fully functional (as in 4.5GH with no hardware errors) K16 board and asked $80 for it - I would not buy it at this point.

Again - https://docs.google.com/spreadsheet/ccc?key=0Ah7ZJVoobFY7dDRGQk1kdmJmaUJwZENKZUdNejJlWEE#gid=0

Realistically if you start mining today, a K16 might produce 0.5BTC before it hits electricity/reward break point.