What it could be...
Sniping system is done great, you have gravity, wind, hart beat that effects your sniping and bullet path, and nicely done camera that follows the bullet if you have a head shoot, moving target, or so. Great. Until you make 1st kill. From moment you do that everything goes down. Because no matter how well you are hidden enemies will be instantly aware of your position after your 1st shoot, and what should be your greatest advantage in the game was brought to zero; some enemies with machine guns will in FACT be more precise that snipers, and will have no problem killing you form 50-100m (and they usually will come in that range, just come form no where), so sniping them will be extremely hard.
A good game puts you in difficult positions but offers you a way out of it, so you don't save and load to much, so you don't get bored.
But that is not the case here. Enemies will attack you instantly after your 1st shoot, will be ultra precise, and will come literally form no where. So the only way you will be able to end it is by constantly saving and loading and trying over and over again. Which is boring and frustrating.
After playing game I have a feeling like half of the game makers worked on stealth sniper game while other half worked on FPS. It is a shame really it could be great.