You should really buy something else than the supplies provided with the units from Bitmain... The factory supplies gets worringly hot and my U3 on a new and better supply is more stable.
(Sorry mikestang;)
What PSU would you recommend? I'm only getting ~48 GH/S with defaults. And that's with a good USB cable to a powered hub.
Get a 4-pin molex to barrel plug connector and use your computer's psu, or if you have any other miners using atx psu tap into that. The U3 needs about 1 watt/gh.