The miners are waaaay to expensive to make even close to positive ROI, if we would have it today it would take almost 5 months (payed in $) with no increase in difficulty (impossible). And the delivery date is in Q4 2015, game over.
Most expensive miner, 1.8 GHS.
currently 0.2-0.35 BTC per GH/S per 24 hour.
How do you mean, 5 months for roi?