At a diff increase of 18%, $.15kwh, 500gh, 400watt the S3 mines less than 1 BTC before it operates in the RED, if it starts mining today. And that is after 179 days of exposure to the risk that the network hash rate won't go ballistic.
There is absolutely no way anyone in their right mind should consider paying 1 BTC for an S3
the difficulty increases are no longer 18%/jump. Its closer to 14%/jump if you average the last 5 or so, and its visibly decreasing. (the network is no longer doubling every month - not sure if anyone noticed it now takes 7-10 weeks per doubling)
I would pay 1BTC for an S3 - possibly up to 1.1BTC if it DELIVERS before the end of June.
IMO, they need a larger S4 device similar to the S2 but better optimized for hashrate and without the shipping issues. If they could pack 4TH/3.5kW into a 4U case for ~8BTC i would be very interested. These little <1TH machines will very soon be worth less than $100 each and will require large awkward stacks of them ziptied together if anyone wants to operate a farm with over $10,000 of equipment
The SP30 will be 6TH / 2.8kW / 2U very soon - bitmain needs a similar pro-level mining device. The S2 wasn't terrible, but the chips were a little
too undervolted and the unit wasn't built well for shipping with fumbly couriers that kick or drop their cargo.