After levelling my char to 85, i realized that i did enjoy levelling to 85. However, I have to say i enjoyed it purely because I wanted to follow the storyline of each zone, which is well made and develops well as your char progresses.
However, compared to WotLK... no more elite quests... those quests that sometimes require 2 or 3 players to fulfill. I loved these quests because normally i tried them alone (sometimes wasnt doable) but still, they provided much more emotion than the ones we have now... Let's face it, questing now from 80-85 is great with the first character, however, I am a little afraid of what will happen when i level my alts...
In short: For the future, giving those last quests of each chain some more difficulty. That's all.