The two zones definitely helped out on questing - also the various quest hubs in the zone (i.e. Fizzcrank's Airstrip, the DEHTA quests) made it easier so you could go to another one if one area was particularly crowded. As for gear changes most of my alts had gear from Karazhan or crafted gear equivalent (i.e. Primal Mooncloth and Spellfire sets) and so far have not had to replace pieces except for neck and rings.
There's a lot of cool stuff coming - my biggest concern is with 10 characters all at 71+ (yes I play too much) are they going to increase the slots available per server. I like that they are filling in the old world and doing a lot of stuff along those lines...it will be interesting to see what happens. As with Malygos and Arthas for Wrath I like that Deathwing is the main villain of Cataclysm.