price is still to high 
+1
S1s are now about $200 a pop. For those who are math challenged, that's $1200/TH unpowered or $1560/TH stock with ATX golds.
Sorry to say but price (including costs of PS) and power consumption is not the only means of comparison for product value between S1<>S2.
When Bitmain can also make the S2 as reliable as the S1 and ship it in working order to customers with a lower sale price then I will take notice.
S1 is awesome; Bitmain should think about moving to 28nm or 40nm in the same great form factor for ~400-500 GH/s and =<1w/GH.
That would be a killer product up to $400-450.
IIRC there was already rumour, or an outright statement by Bitmain that they've got a 28nm in the pipeline.