When I bough my CYMA M14 I was pretty skeptical, but I don't regret it. It's one of the many guns I've bought without regretting. Dis assebly is a major pain, but there barrel length and surprising amount of compatibility with standard V2s. My only complaints are
Trigger wouldn't puch back after shooting (Factory lemon. Newly manufactured versions dont have this problem
Proprietary barrel. You cans till find a lot of barrels for the M14.
Poprietary (spur?) gear. I think it's the spur. Could be a different one. Not a big deal at all. unless you're making this a godly setup, shouldn't matter
Other then that, they're pretty good stock. I'm currently running it with just proper shimmng and new grease, and an M90 spring for gaming it indoors until outdoor season.
"This is the kind of grease I'd put in my girlfriend"