Just received two S+ batch 11's that had the 11/26 firmware on them.  Problems I had were:

1)  Each unit would not exceed 250GH/S.
2)  After a random amount of time rate would drop to between 20-50GH/S and stay there no matter what pool/balance I put them on.
3)  Random boards/chips going to 'x'.

I flashed back to 10/24 and now I'm getting 450GH/S consistently without any 'x'.  Definitely seems the 10/24 firmware is solid from a performance/stability perspective.

Mowpow