I imagine it'll take a lot of work/thought to redo the character models. Can't overdo things to the point where people dislike the new look.
I also like the idea of being able to change the look of items. I still have some "mementos" from each era of WoW and might go with the old Warlord's PvP set look.
EQ changed the look of everything essentially with one expantion. The outcry was massive but very short lived. I think WoW would be ok if they did some make overs.