BFL is full of shit. Nothing has changed within the company. BFL saw a real company (Enterpoint) come to market with a product at the same price with double (quadruple?) the efficiency of the single. Around the same time, some very clever bitstream developers (eldentyrell and bitfury) brought the performance of the Spartans up significantly so that even boards with 2 Spartans could get closer to what the Single offered (mh/s wise) while being much more efficient.
Just to keep statements accurate. (The lack of which, IMO, is our biggest complaint against BFL.)
1) The Enterpoint product currently costs more. And will soon cost even more more.
About 8% more until the end of June. 63% more starting in July.
2) The Enterpoint product currently *matches* the BFL single on a MH/w basis.
IIRC, the best currently being delivered is about 400mh/s at 40w using two of the four FPGAs. About 200mh/s when using all four.
In the future the Enterpoint product *might* be double with 800+ at 40 to 50w.
But that is a future / hypothetical situation. *After* that is achieved it will be legitimate to sing their praises. (While acknowledging that all the BFL competitors, at that future point in time, cost greater than 50% more at the entry point level.)
3) IIRC, the best that has been achieved on Spartans is about 250mh/s per FPGA. Two times that for 500mh/s is substantially less than the BFL Single 800+mh/s. And, again IIRC, the other bitstreams you refer to are not generally available for use.