I looked at those a month or two back, but I went with this one instead.
http://palmettostatearmory.com/index...ght-upper.html
Granted my efforts were to build a mid length lightweight rig on the cheap. Mine's mated with the cheapest lower around, a new frontier polymer lw-15. I put my oem trigger group in it from another build, swapped out the base plate for one with a sling adapter, added a tactical latch, and I was done. It's surprisingly solid and has 50 flawless/function check rounds through it. I'll be putting a thousand rounds through it in October (if not sooner) and I'll report back.