The Grumpy Elf has some very thought-provoking posts up on his blog, A New Leveling Model and Is the Leveling Model Dated in particular caught my eye. I do like a lot of what he's advocating, but I'd like to offer a caveat (well, two actually).
Talents - One of the reasons for gradually unlocking spells and abilities is to let new players get accustomed to them. I don't know about you, but I use more than 4 abilities when playing. Hell, I have more than 20 abilities usually mapped to my left hand, and those are the ones that I consider using regularly, or at least in specific situations that pop up fairly often. Granted, I have an odd setup, using 1-6, Q-T, A-G,Z-B, hitting all of them with my left hand, with a bunch of them having Alt functions macro bound to them. My right hand is used for movement and target selection with the mouse.
Dumping all the spells available to an 85 on a fresh new player would be overwhelming, especially if they used the default WASD setup that Blizzard gives them. "I'm supposed to use ALL of these spells? How am I supposed to hit them if my left hand is stuck hitting those 4 keys??? Bugger this, I'm gonna go play Farmville instead!"
Altoholics - I have 30 toons that I am un-concentrated on leveling, at a veryyy relaxed pace. I would like to offer an extension of the Grumpy Elf's thoughts, in that quests/reputations credit should be account wide if this new model goes through. I've got 8 85's, and have only done the Tol Barad dailies to completion on 6 of them. Since all your toons would be level 85, gear would not be over-powered, so there would no reason for currency that one toon has acquired not to be used by others. For example, the Crocolisk daily in Tol Barad is slightly irritating for me to do, since I want to skin the damn things for Savage Leather. But my priest Burizadokyan(JC/Alch) and warlock Bonescourge (Scribe/Eng) can't do that, and it wouldn't be feasible to log out, and log back in with my skinner. Since my rogue Thrillkiller is my skinner, and has done everything I want to do in Tol Barad, why not allow him to gain Tol Barad Commendations, and let Bone or Bur spend them? You could have an account wide reputation level, but you'd still have to put in the time to do dailies on at least one toon for the currency. You could do the dailies on more than one toon if wanted/needed, but...speaking from experience, that wears you down and burns you out.
Anyways, those are my thoughts. Cheers!