This.
Agreed.
This.
As seems to be typical of these Chinese firearms, each batch that comes in seems to be a little bit better. The 13xx serial numbers seemed fraught with problems. My 14xx functioned reliably but the sight rail was out of alignment slightly. I have a 15xx now, and it looks to be perfectly built and actually has better springs than previous models, and the chamber mouth is "funneled" a bit (not sure of the correct term) for more reliable feeding. You can get them for ~$800 new in some places and I think that's a fair price.
The only mods I've ever had to do were because the magazine well was a little tight for some of my polymer mags (Not the magpuls, though!) Nothing a few minutes with a hand file couldn't fix.