Buying Cheap Meat in Asian Groceries - SEA I.D.

Apart from Uwajimaya, how would you rate the quality of meat found in Asian groceries such as Viet Wah, Hau Hau Market, Hop Thanh, etc. The prices are unbelievably low, and I'm wondering whether it's a case of "if it's too good to be true it probably is."

At Viet Wah and others, I have seen packages of beef marked "ungraded" by USDA - in particular I am wondering whether this is safe to eat, let alone whether it will yield good flavor. Does anyone know the story of where these places get their meat, or why they don't fall under USDA standards?