I've bought from them twice and a friend bought from them once. I won't do it again and neither will he.
One upper I got had a rough, tight chamber that would freeze the gun after any sort of use (had to tap out cases with a cleaning rod after shooting more than a magazine). Sold it for real cheap to a guy who was willing to get it fixed.
A "complete lower parts kit" was missing the buffer. Bought a new one from Bushmaster.
My friend's "complete lower parts kit" had a broken trigger pin (finished, no less). When I emailed them about it (and informed them of my previous experiences), they said they would replace the pin after I sent them my mailing address. Sent it and never heard from them again.
So far they're oh and three in my book and they've never made an attempt at fixing things, so I'll go elsewhere.