I had a TM famas. The biggest problem it has is that if anything breaks you are sol. As people have said, the motor is an older kind that fits into the gearbox shell with no room to expand upon it. The motor cannot take very high powered springs, but an m100 should be fine. Some of the parts in the box can be replaced with v2 parts, but not all. The motor is the limiting factor. I had a magazine latch break on mine and being unable to buy any replacement parts, I stripped it and sold the pieces. The Famas is defiantly not a piece of shit and I would really like to buy one again. The JP on the other hand is an OLD clone, before clone makers got their shit together, so steer clear of that.
EDIT*
I saw the beating you took on AA. It is plasticy, but the hop up doesn't really suck that much.