the jg g36 is a good gun if you get the newest revision of it. The only drawback of it is the hop up design is their own. If you know the guys from the store and they have seen and worked on g36s before.. (and this is where you're buying it from presumably) you should be able to take 1 pin out of the magwell and pull the magwell off to look at the hop up unit. If it looks like a big L shape, it's the newer model, if it looks like the straight marui style, then it's the old one.
The new model is pretty beefy as china guns go.. they're built well enough, with a nylon fiber body, unlike the older ones which were like TM, made from ABS. There's a breed of gun builders out there that buy JG guns as base guns to build monsters out of because they're very affordable. Their reviews of the gearbox internals put them on par with combat machines from G&G.
They're both entry level guns, so don't expect the world from them.... and even then.. don't expect the world from any gun out of the box, entry level or premium.
I futz with V2s, V3s and V6s. I could be wrong... but probably, most likely not, as far as I know.