The bad first: You have limited saves per mission and the enemy AI has perfect accuracy at any range. Often they get one shot, one kill. Even when patched this game crashes to the desktop more frequently than it should. Especially in later missions.
The good: the sniping mechanics are pretty good, once you get used to using hit & run tactics. The maps are usually large with good cover. In a typical mission you find a good vantage point, assess the enemy patrol route via binoculars and thermal imaging, then pick off one or two guys, infiltrate and try to find a good sniping position to lower the odds against you.