The sense of nostalgia for the old will hit at some point, but maybe not for months (years?). Right now it's all new and exploring it is a lot of fun. I have a level 21 shaman that I intend to level up so she can run with my team of four level 31 warlocks, and I'm looking forward to doing so through new quests and content. I only got to do a bit of running around last night on my 80 shaman and didn't get to see much, but I loved it all. Spent the first half of my evening doing a bunch of upgrades to my computer and am able to run graphics at ultra now, which makes it even better.