I did a buy on the S4's and their hashrate locally is 2th/s or greater (awesome!) however, when connected to BTCGuild NONE of them show anywhere close to 2 Th/s. They show more like 200 Gh/s. I have 2 that are over 1 Th/s, but the rest between 0 - 278 GH/s. WTF Bitmain?
The fix for now is to use GHash or BTCGuild with 2048 difficulty. Pools with vardiff seem to overload the miners at the start when spamming them with difficulty 16 shares. A new firmware is on the way soonTM.