There are a couple differences I can name, but thats only because I play with these classes allof the time. Classes like monks, rogues, bruisers, assassins, I don't know much about.
I see more warriors use shields than duel wield. And no not because they have Anger III on them.
Shamans cast something called 'Wards' which is basically a rune that absorbs damage, and costs no components, but they still slow, and heal.
Bards don't continously play songs, they play their song like a buff, when it wears off they play it again.
There is alot of the same too.
I dont think Paladins and SK's can duel wield. I see them use 2handers all of the time.
Clerics basically just heal, heal, and heal still
Enchanters mez, and breeze.
Druids still suck...
Except for the large amount of quests, and sweet graphics, it's basically the same ol' level grind, and "I have to prove to others that my EQ penis is as big if not bigger than theirs." So basically pick a class that semi-interests you, then try to show everyone else how late you can stay up and press buttons. Oh and don't be an idiot...I hate idiots.