I just bought a Century STG 58. finish is so-so(typical for Century). The top cover has a big ding in it(easily replaced). However, the big reason I bought it is due to the Imbel receiver. I now have a shooter, and when funds are available, I have a great platform to build from.
If you have the bucks, the DSA is the current "cats meow". If you are limited, the Century guns are a crap shoot, but if you like to tinker(like me), then its not a bad route to go. And like Larry pointed out, even if you send it to Azex, you are still into the weapon a whole lot cheaper.
Inch vs. Metric: At one time, I would say Metric is the only way to go. Parts are plentiful, as well as mags. Currently it seems alot of inch parts/mags/guns have become available lately, so inch isn't quite the disadvantage it once was(for now at least).
Zane