a lot of people do get all misty eyed and look upon vanilla and tbc with rose tinted specs but a lot of that is with good reason. A quick jot down on what I liked about vanilla and tbc:
*World pvp was alive and kicking and due to this the world felt alive and vibrant.
*The lore was so much better during this period too.
*Questing wasn't so 'on rails' as it is now, you actually had a choice of what quests you wanted to do in each zone if you wished, and because of this there were some truely epic quest chains.
*Class quests!
*The classes actually all felt very different, homoganisation hadn't become the norm.
*Talent trees / points every level, I know some didn't like this but for me (and many like me), the freedom that the old system offered was a cut above the locked in abomination thats on offer now and coming in Mists.
Essentially you had choices, or an illusion of choice, that is no longer true. Choice is king in MMO's and for me it's no surprise that as Blizzard have whittled away those choices the player base have voted and left their game.