Yea. Scale can be a huge problem aswell, its nice to have a huge world to explore but sometimes its just too big, and it seems this one will have more terrain to explore than Far Cry 2 and I thought that was already too much.
As long as you do something interesting with the world, that shouldn't be a problem.
The problem with Far Cry 2 is that its being touted as a action game, but the game is actually 90% walking\driving through african wilderness in hopes of getting to action and 10% action. In FC2, you simply have to explore: you have to go on ridiculous walks\drives in order to get to your next objective, and the problem is that there is nothing to do in between (aside from getting shot on sight by guard checkposts). The exploration therefore seems like booring work, before you get to the good part - the action.
As long as you dont have to walk ridiculous lenghts in order to get to action, huge world should not pose any problems.