FYI I just got one today, after 20 minutes it gets to 2.06 Gh/s with clock=x0981, and it runs great with zero errors and zero rejects.
When I overclock to 0A18, which on the U1 is 2.2 Gh/s, after running for 20 minutes it only gets up to 2.12 Gh/s with 0 rejects and 5.41% error rate.
So, it seems like 2.0 Gh/s is the max you can expect with low error rate.
I haven't been able to find a user manual on the U2 yet however, and the clock parameters for overclocking may be totally different than what was used for the U1.
I have emailed Antmain about this but have not heard back yet.
Edited to add:
After 2 hours it's hashing at 2.063 Gh/s, with zero rejects and zero H/W errors.
Also, FYI my USB power is not an issue. I am getting my +5V from the molex connector of an ATX PSU at 32Amps.
could you try 262.50 MHz | 2100 MHs | 0A01 | 020 ms for us on the U2s its the clock for 2.1 gh/s also there are know clock speeds for 2.05 and 2.15 if there is a finer limit to thier ablites
yeah maybe they can do 2.1 with little errors and no fan.
funny I wonder if holding the old ones may be a good idea.
the new heat sink is so big. if you have the 49 port hub you will only fit 28 or so sticks. while the one sticks can fit the full 49. right now I have 30 old ones. I will wait for some users on the new sticks to talk about them before I order some u-2s.
I have 30 ice fury sticks with bigger heat sinks they clock to 2.5 or 2.6 cost a lot more but I have had them since jan 1. I think I will hold them as they hash at a higher rate.