Fuck Bards. I hate the concept.
I think that Clerics are already pretty good Fighters (heavy armor, solid hit points, and relatively cheap advancement with a middling attack progression, even if they're mediocre in the weapons department), so that leaves limited real estate for Paladins.
On the subject of Clerics, I don't personally find Christian-themed religious guys to be very interesting, but role-wise, they certainly fit into the game.
As for Assassins, I like the concept, but they can be a bit crowded by their similarity to Thieves, at least they way they tend to be done.
Barbarians are also a matter of execution, but it's nice to have a Fighter alternative.
I'm a big fan of Rangers as outdoor skillsters.
Druids are an interesting concept, but the execution usually feels a bit off to me.
Race-as-class Dwarves and Halflings are a bit too close to Fighters for my taste, but I'm okay with the concepts. I'd just want to make them a bit more distinct. Halflings should probably move a bit more in the direction of Fighter/Thieves, and Dwarves should maybe pick up some of the mechanical aspects of Thieves (dealing with traps, opening locks and so forth). In addition to maybe some unique stuff, that is.
Elves are great as Fighter/Magic-Users, though they tend to be a bit overpowered. Magic-Users could use a larger repertoire of spells starting off (just 1 spell per day is bullshit), and maybe get a bit out of hand at higher levels, but they're certainly interesting. I guess I've got a bit of a swords & sorcery bent though, and the extreme specialization on spells and uselessness in combat is a bit much for me. If I had designed the game, they'd be halfway towards Fighter/Magic-Users.
Fighters are solid, as long as you've got a good GM who isn't afraid to improvise modifiers and be colorfully descriptive.