I've been on a 42-1 killstreak on Fallen Fighters with the sniper rifle some time ago. With all the fog around, the scope provided a much clearer picture of all the enemies camping in the windows of the univermag building.
Needless to say that I picked them off one by one, the entire team was in panic because they simply could not cap the objective without several of them dying.
Eventually, a large number of people who had intended to camp that round, proceeded to go for the objectives.
You could really see that they tried, they mass rushed the objectives and were really doing a great job on the final pushes. Unfortunately for them, my team simply had the higher amount of tickets.
It happened just once, but I am pretty sure that I would not have made the same 220+ meter shots as fast with a standard rifle. And while I never did get the same killstreak again, I have been succesful sniping on Pavlov's house, Barracks and Spartanovka.
Every map however forced a very different style of marksmanship. On Barracks I needed to make good use of the shadows and huge craters that the map provided. On Fallen Fighters you need to take in account the angle of the sun, so you remain unseen and on Spartanovka it is important that you make proper use of all the little peekholes in the wood while scouting the map for unexpected places to be in.
Marksman is by far the second hardest class(AT-soldier being the hardest). I'd say that if you want to take a sniper role, you need a good understanding of positioning yourself in games. As you want to remain undetected so you don't need to waste too much time relocating.
Also getting the optimum angle to flank an enemy while making sure that you don't overexpose yourself, is a very hard thing to do. But if you manage to succeed, then it's an absolute joy seeing the enemy be utterly confused where the shots are coming from. They start doing all kinds of things, zigzagging, attempting to bunnyhop, pronediving. But then you take a deep breath, and let them think you're not picking them off for a little while and you shoot them whenever they peek out again.
Psychological warfare at it's best!