GBBR's are a lot of fun...but I don't think that they're ready for prime time play every game yet. Either for reliability/durability or power reasons. Maybe...hope so. Jeez they're fun....
Compared to real steel...well, I can't shoot real steel whenever I want in the my basement in the middle of the GTA. I really like the convenience of blowing through a couple of hundred rounds (drills, testing or just mucking about). I shudder to think of the post-gun costs that I would have incurred to date if I shot the same amount of real steel in lieu of airsoft. Not blowing your friends to bloody bits for good is a nice touch.
There's some tried and tested PTW packages showing up on the classifieds for $900 shipped. You might have to shop around or wheel and deal a bit...but they're there. That's a pretty good deal.
A nice "good old" AEG (not the hybrid stuff common today...not the JG/A&K stuff)...with decent upgrades, will put you close to that same amount.
At the end of the day you've got to go with what you want, what you can afford and what you feel most comfortable with. That may be a "traditional" AEG, a PTW, a GBBR, bolt action, SAA revolver or sling shot for what anyone else cares.