I have a M4gery that I built up using a Mega upper and lower. I also have a Stinger lower, which is made by the same company, just an earlier version. It is my understanding that some of the very early ones were a bit tight in the mag wells, but even my Stinger lower is fine with all of my mags. I also don't know the whole story, but I believe they also make OLY lowers and someone elses lowers off the same equipment. I don't want to get into a big OLY debate here.
My Opinion:
I personally LOVE mine and think every one I've handled is great. I am planning on purchasing another MEGA Gator and pistol lower next week. The black on them is VERY dark and the machining is pretty dam good. Other than maybe trying out a Stag lower, I will probably use them for most of my future builds. Pardon the pun, but I'm into the best bang for the buck and I think they are it. Not to mention, I like supporting the local guys. And guys, I'm not connected with Mega but wish I was........
I will at some point get photos to post, but in the mean time there is another post you might want to check out:
MEGA Photos ThreadHope this helps,
Nox