I've always loved the levelling experience. And I've levelled numerous characters to 70. From there on, it dies down completely for me. I just can't stand the boring quests and zones of Northrend. I've managed to level to characters to 80, and that's it. I've wanted to level more of my alts to end game, and I have a bunch of them at around 70-75 but I just can't get past the boring linear questing of the Northrend zones.

Personally I find the questing past 60 much better than before because it's much less of a headache to keep running between opposite ends of the map, but you have different tastes I suppose.

Hehe, yeah. The running between opposite ends of the map is something I really enjoy. :) Improves the feeling of adventure, I suppose. Also, I like when you can do the quests after your choosing. I can improve my routes and at what order I do the quests each time I level a new character. But in Northrend, there's little choice and you end up doing the quests pretty much the exact same way you did last time.