As a former AUG owner, I must say that the Marui AUG is hands down one of if not THE best airsoft gun for beginner to serious airsofter.
As someone else mentioned, the military model does NOT have a lot of scope options, though the built in scope is really great for field use. You do not need more than what the military scope provides as far as magnification. If you plan on keeping the FS low for CQB games, definitely go with the civilian model and get a cheap red dot.
Someone mentioned that upgrades can get pricey. They must be talking about the flashy external upgrades like the shadow mod etc. Internal upgrades are no more than upgrading any other AEG. I only ever bought 1 external upgrade and that was an extended HBar barrel that ran $80.
Everytime I have to monkey with a colt AEG(Classic Mistake or Tokyo Patooie), I looooonng for the days of modifying my AUG and its V3 gearbox.
While I owned them, I owned 4 different ones. One civilian had a stock FPS though silenced with silencer replacing the exposed barrel. Another was a shortened barrel military that I used at Operation Restore Order, shot 350 FPS. I had another military tuned to 400. I had an HBAR barrel that I could put on either one, actually any of them. The last was set up as a sniper rifle at just under 500 FPS with a special mod to make is semi-auto only. I could change out any barrel for any other due to the realistic breakdown of the gun.
The weight is kind of misleading. I am not sure that it is really any heavier fully loaded than a fully loaded M16 or M4 with a large battery. The trick is that the bullpup configuration puts the weight behind the main grip. If you're shooting from the hip or off the shoulder, this will be awkward. If you fire it realistically with the stock against your shoulder, you do not notice the different weighting.
Another "problem" that I never had happen to me is that the foregrip breaks easy. I never came close to having this happen. The only way I can see it breaking is if you pull back heavily on the foregrip like a moron. or drop your gun so that it lands pushing the foregrip back...like a moron. The foregrip is sweet. You can put it down and have a foregrip just like someone that paid extra to have an RIS on their M4. Or, you can leave it up to act as a rest like someone would hold an M16.
Mag prices are not that much different than for other AEGs.
I have since switched to using colt modelled rifles for sim reasons only. When I was using the AUG, I was pretending I was an Irish soldier in some bizarre exchange program. After typing all this, I am again within a springer's range distance of selling all my Colt-style guns and buying an AUG again.