If you're not used to PC games, then perhaps your missing the aim assist which the consoles have. Or maybe, you have your sensitivity too high or low?
I find it much easier on PC than PS3, but I've spent waaay more hours playing PC games than console ones.
I find this the hardest cod for sniping, probally because i dont have a really good pc, i can still run the game in 80 fps.
It seems the hardest to because my playstyle is really different, if you want to play some private matches sniping add me on steam : Saturnz is my steam and im from the netherlands.
Definitely easier than in Black Ops 1. I can't snipe at all on consoles, but on PC I find it very easy.
But maybe its because my last console was PS2.
First you need to find the sensitivity that you are most comfortable to play with.
There is no aim assit on PC, but mouse is 100x more accurate to aim with and responds sharply to every slight movement you make.
In Black Ops 1 you had to get familiar with the crosshairs waving back and forth for a while when starting to aim down with the scope. But this ofcourse only effected you when trying to quickly kill target on close range like in the video below and not the real sniping where you don't need to rush with aiming.
You shouldn't have problems with Black Ops 2 sniping after you find the sensitivity you like.
Sniping properly like a sniper should be is definitely easier than on consoles but Quickscoping and dragscoping is an art form in my opinion when it becomes mastered on pc. Without Aim assist you over/under correct your shots a vast majority of the time at first because of no aim assist and is what makes it the hardest thing to do on the pc version.
Ill admit even ive taken up Quick/Drag scoping over normal sniping because of how much of a challenge it is compared to other CoD's (with BO1 being the exception) and for me when i changed from spray and pray hit everything at any range SMG's to trying to Quickscope it was a very refreshing challenge for me (with the occassional use of AR's if i need to step up my game to help my team more to push harder towards objectives.)