once you do the standard AEG piston/sector gear mod, they are as reliable as any other AEG. and that mod is only advisable if you don't want the pre-cocking feature or you want a high speed setup
Hop unit needed some love to get the trajectory down, wire crimps snapped at the motor connection (bit of solder fixed it) gearbox locked up and blew the fuse (my own fault really)
Like i said, nothing difficult and nothing that cant be fixed with simple tools and a bit of TLC
All said, ive probably spent more time cleaning my two gas guns after each game (a 20 minute job per day) than i have fixing my aeg, and ive owned the AEG over a month longer than even my oldest gas gun.
I dont think any of the problems ive had would be too dificult for anyone, and the short time i spent tinkering taught me alot about how my gun works, and if it should ever break down, ill have some knowledge to help fix it.
I wont lie if you are nervous about tinkering, there are more reliable guns out there, but that doesnt make the ics unreliable, it just has its strengths elsewhere.
And as said earlier, a gas gun (pistols aside) isnt a great first gun. As fun as they are (im a convert myself) they are much more work and less practical.
I have the G&G L85. No real problems. I've disabled blow back feature as it can ruin the piston. I'm currently trying to sort the semi auto lock up issue which seems to be a problem on all l85s, although it's not a huge issue for me. The gun has a split gear box and is incredibly easy to open and work on even for me. It has a really nice range and accuracy and I haven't even done any real modifications yet.