Love my Cyma G18c, its hard to get a holster for AEP's because they are a slightly different size to the real thing or the gas versions. I've now made a custom kydex holster for mine and its snug.
I haven't had any problems with the parts, although sourcing them can be hard, and I cant locate many upgrade parts. It's never skipped a beat. Its pretty bomb proof. It works when its cold when gas guns are failing. But it isn't the highest powered anyway, mine was 200fps out of the box but it works fine. The trigger delay can be a problem but if you get the LiPo batteries its a much shorter delay.
My only other issue is that the standard mags are small and a bit fiddly which can make speed reloads a bit of a problem. I've never tried the 100rnd ones but they look like a laugh.