Consider this: Even if 100% of the network suddenly replaced their GPUs with FPGA, come December the block reward gets cut in half and the Single will be generating $1.50/day (assuming today's difficulty and BTC/USD exchange). That gives it a 400-day payback period. Is that good? Not particularly.
yeah, but there are still ~300 days until the approximate time when the reward will be halved to 25btc.
If you are planning to mine with a Single, there are only 300 days if you ordered it back in November and it arrives now. People ordering today will not see it for 2 months. Then there will be 250 days left.
yeah, i thought about the production delays as i was posting. hopefully many of the production kinks have been worked out, and they will be in a position to start delivering in a quicker more efficient manner.
regardless though, as long as you can get a unit in the next few months, you should be able to take a huge chunk off the time to payback prior to the adjustment.
Great to see proper discussion instead of just inane comments from bored people. Looking forward to the community working together to improve the software over time 
