Well, I have one on a G19 frame and 2 fully custom 80 percents. None of em spit brass on top of my head, they all spit it out like my M&Ps. People who deal with ejection issues usually have the gen 4 ejector and need to replace it. So that is actually a Glock issue and has nothing to do with 80 percent builds.Thing is that they really don't feel like Glocks and you can build it to whatever quality level you want. Still eject brass on top of your head though...
As far as how they feel. The reason I build em is exactly because I hate how a glock feels. For the one Glock frame I do have, I bought the back strap that sits above the curve and makes it straiter. Now I love it.
Either way, to each his own.