After spending 7+ hours playing I have found the following a bit of a bother:
1. The TTK is way too low and you die too fast. My personal suggestion is to increase it a little bit, it will slow the game down a bit and make it a bit more tactical on the long run.
2. The recoil is almost non-existent. Again, in my opinion, that should be increased a bit, especially when using scope - instead of spraying, you should be required to tap or burst... or both.
3. Proning (or dropping to the ground, or whatever it's called) literally sucks and it's ruining the game. The animation is too fast and the perfect aim you get from it is way too unfair. Every match I join, I see at least a couple of people spamming and abusing this mechanic.
Other than those three (I can live with 1. and 2.) the game is fantastic, I can see dumping hundreds, if not thousands of hours into it. I adore it, it's simply amazing!