My JG AK47 beta is shooting at an average of 390fps (chrono reading). The exterior finishing is okay, but the internals machining quality, as pointed out by Coma, is less than ideal. But for the price (roughly 100CAD in Hong Kong), I would say it's pretty good bang for the buck.
In terms of long-term reliability, I can only say this: if you know how to do your own gunsmithing and have some spare parts sitting around. It is not an issue at all.
"Assumption is the mother of all fuck-up's."