I played Druid for the first year in Vanilla (before the switch to Lock and the "OMFG! New Level. Got Death Coil. Can PWN in PVP now!"). It's true, that levelling feral (after 1.6?) was easy except maybe in StV with all the rogues. Especially because you were able to adopt and change forms. Or situations like ... a mob which is only killable by 2 players, the other one is DPS and you just switch to healer gear and both were successfull because of that.
But the downside... For PVP you won't get the raiding gear because of feral were not allowed there. So you had to do things like getting excalted in AV for the mace or you had to farm for a gearpiece in Darkmoon Faire. And for raiding ... respec to Resto.
Not sure, if I level a druid for Nostalgia ... or warlock ... or priest (Shadow in PVP).