I really hope the classes don't ruin this for me. Ill have to wait and see I guess. Still picking it up for PC for the campaign and MP at least.
My biggest concern though is MP in general on PC. I'd imagine most copies will be sold on XBO so Im not sure how long the PC MP community will last.
I was a bit worried about the classes in horde before I saw it in action as well. After watching a lot of the gameplay though, I'm extremely hyped for it. It doesn't really restrict a class from doing anything other classes can do, it just gives certain classes added benefits for certain things.
I'd suggest watching the First to 50 thing they had a couple weeks back, gives you a much better picture of the classes in action.