The CMMG deal is good for somebody who is on a very very very tight budget. I have seen barrels and barrels of these exact ARs at our local gun shows. I gaurantee that one of these could very easily be cleaned up and turned in to a nice beater/trunk type gun, none of them are safe queens..........but for $550 what do you expect? The only problem I have is that for just over $550 you could build a NEW AR. I would drop the $550 in a heart beat if I could choose one of the CMMG rifles from the bargin bin, however I wouldnt for a DPMS.
ETA- IIRC, all the flaws on the rifles in the bargin bins are circled, so you know what the problem is. I remember at one time seeing rifles with roll marks that were just bairly stamped or the stamp didnt stamp correctly. example: I saw a DPMS rifle where the panther stamp didnt come out correctly, from 3 feet away you would never know the difference. Most of the rifles seemd to have at least a few light marks on them, but nothing you couldnt clean up! Good luck!