Sniper is not an adventure for those unready for some serious combat in some strange environments. Playing this with my party, we met neither of those conditions and payed for it dearly.
The adventure is quite linear in execution, and some of the combats did not make sense. There was ambushes in places that were unlikely and foes cohabiting places that didn't make sense (animals and things that make animals flee, for instance). A clever party could make things much easier by thinking outside the authors box.
In addition, my GM informed me that the several of the challenges were well above CR, although I did not verify the calculations. I like a good fight, and if you like one too this is a good adventure. If you like complex plot, go elsewhere.