For me, Nasus' big problem is the fact that he desperately needs farm, arguably moreso than any other champ, but at the same time it's very easy to push Nasus out of lane. He's easily kited and zoned, and the fewer minions he gets the less useful he'll be.
Of course, if Nasus ends up getting a passive lane or a melee champion who can't duel him, then he stomps hard. Personally I find him really fun and I think there's a lot of potential for him to become FotM in the near future. --- Cooler than Freddie Jackson sippin' a milkshake in a snowstorm.