love this gun. pretty versatile, range is great, stock fps with .2s is about 390. only real problems are the rail and the bushings.
The Bushings are brass, so they are not very strong(granted ive been using it since early November of 2013 and they are still working) but I would recommend getting steel bushings. which is another issue. It is near impossible to find non-bearing 8mm bushings from well known parts brands(well known being important to me cause I can ask about reliability and find reviews.)
now the thing about the rail, is that there are only rails on the ends(front of the system and back of the system near magwell) on except for the top. only way to get the rail pieces is to order them from dytac. also the rail, should you feel the need to replace it(don't, its lighter than hell) u need a special rench(not a delta ring wrench) to take it off. the is the ONLY way to do it. you can remove the bottom half by allen keys. just remove the screws and push the pin on the bottom near the mag well.
other than those, the other issues are very minor and are just an issue of breaking in the gun. I really love this dmr though.
blowback is nice (many compliments and very distinct)
removable flash hider
brass bushings(should replace whenever possible)
battery compartment not very long(but the stocks adjustable and I have long arms so it doesn't bother me
buttplate is hard to get off(not a con just annoying as hell, but atleast I know it wont fall off)
minimal mag wobble(I use king arm mags and the stock mag, but electrical tape in the magwell fixes that easy)