I'm really looking forward to Mists of Pandaria becoming more reminiscent of the questing experience prior to Cataclysm, while still having some linear story lines that can involve the player in the more epic events of the zone.
As a bit of an altoholic, I'm noticing that the revamped 1-60 areas and the Cataclysm linear questing zones are extremely fun the first time around, and quite boring the second time around. I already know what happens in the zone, yet I have to do every single quest in the exact same order and way when I take a second character through that zone.
While Outland and Northrend quests are ones I've done repeatedly, I still have a sense of freedom and enjoyment from being able to choose which quests I accept, and which quests I skip, and still be able to level through the zone. It allows me to better personalize my character's experiences in that zone. For instance, if my character doesn't want to complete a certain quest or help a certain group of people out of principle or RP story, she doesn't have to. My next character, however, may not have the same qualms and will do those quests, and suddenly the zone seems new and fresh as a result.
I enjoy MMOs for their greater sense of freedom and the sense of choice when I level my characters. To go completely linear in questing makes it more of a single-player RPG experience. I don't mind a good single-player RPG, but I do mind it in WoW.
Also, I found Cataclysm questing much less enjoyable than prior expansion questing very much due to the fact that I could not quest very effectively with a friend. I wanted to see a lot of the content with my boyfriend, but found it became very boring. Quests were easy enough solo; with a friend they were too easy. The linear questing also made it imperative we ONLY play together, or we'd get out of phase with each other and have to catch up. Prior to Cataclysm, I liked that even if he wasn't online, I could go to another area and find some quests to complete by myself, and he could do the same, without affecting the quests we reserved to do together.
It's encouraging to hear that there will be more of a balance between both kinds of questing, and I look forward to seeing what transpires. :)