Firstly, this gun is amazing. There are almost no cons that I can think of as of yet. The build quality is fantastic, and you really feel like you are holding the real thing when you hold it. The only wobble that I could notice was the wobble in the crane stock (which is normal, as even real guns have this), and the wobble of the handguard (which is because it is because it is removable to put in the battery)
The blowback on this thing sounds BEAST. When you fire it people swear that they hear a real gun. The blowback is loud and it is crisp, and it really helps to make an already realistic gun even more realistic.
I did notice a couple of problems with it though. Firstly, not all M4 mags will work in it without some modification. I bought some of the Beta Project mags from this site, and they do not feed correctly. In order to get them to feed, you have to pull them back into the back of the magwell as you are firing (but they look really beast in this gun) Luckily the mag that comes with it works perfectly and is nice and heavy (because it is full metal.)
Also, I found that this gun tends to seize up when there are no bbs feeding into it. You have to constantly make sure that your mag is wound so that it doesn't do this. Luckily all you have to do to fix it is switch the gun to safe and then fire a couple of bbs on semi-auto. I don't know if Javelin designed it to seize up like that so that it would emulate the real thing better (i.e. doesn't fire when there are no rounds), but it can be annoying if you are in an intense firefight.
In conclusion, this gun is amazing. It looks great, feels great, and fires pretty great. I would say that anyone who is looking for a good, realistic gun and is willing to do a little work to make it fire right should get this gun.
Heavy Weight (pro or con, depends on who you are)
Working bolt and bolt catch
Easy access to battery compartment
Awesome looking crane stock
Hard - hitting (ASGI chronoed mine at 385 fps)
Heavy Weight (once again, pro or con)
Slight wobble in handguard
Gun seizes when dry-fired (not really an issue in my opinion, but I listed it anyways)
Some mags don't fit properly in magwell
Rating: [4 of 5 Stars!]