[TaroBear]

The only thing that I can add that many, more knowledge users have left out is the budget thing. In my experience, many more things can go wrong with a GBB than an AEG. Also, if you're planning on upgrade, do it all at once. I made the mistake of thinking I could do it in chunks whenever it fancied me/whenever my budget told me I could. Best just to run it stock, hard as it might be (although it's really okay with a Marui), until you have a substantial amount of cash stashed away, then do it all at once. Otherwise you'll find that many of your upgrades just compliment each other, and if you lack one you're really not getting the benefit of the other.

I went from one of those guys who was "I'd like a nice metal kit for my pistol" to one of those "I need those exact grips and stainless barrel bushing" guys. It's amazing how quickly you'll want to put more into it, and the money certainly stacks up. I know for certain that two of my pistols are easily into the 4 digits now, and they're nowhere near complete or as fancy as the pistols you see in the pistols media threads.