I've actually been playing since it released, but sadly didn't have time to go through the game too much.
I have a lvl 60 Demon Hunter so far, and a lvl 50 Barb. Haven't finished Inferno yet (shame on me) i'm in Act II, but that's what i'm gonna do next. KILL FUCKING DIABLO. Shouldn't be a problem.
I played in a team with a Wiz on the DH and everything solo with the barb. Not that you can't solo it with a DH but sometimes it's funny in a group... Sometimes.
Tried out some Hardcore mode way before the first reached lvl 60. But my internet fucks up and i cba dying just because i got dced. I mean seriously, it's okay to die because you got cornered and raped by elites or walked on a bomb or whatever. That's more like "hey you suck". But when you get a freeze lag or smth like that and die because of it, that's just... way too frustrating.
I have a Hardcore char but i don't know if i dare playing him more! Actually i think Hc mode is kinda addictive, cuz you're like "OK just til the next check point then i stop" but you just CAN'T stop. First you try to pull carefully and in the end i just rush into everything to go as fast as possible. I love that mode more than softcore, i would only play this if my internet was perfect and my laptop wouldn't shut off depending on it's mood.
Don't know much about the other classes, feels like everyone plays a monk because they're so OP. I tried Witch Doctor til lvl 5... I have no clue if i really want more chars, i'm pretty happy with the ones i've got.
My Demon Hunter has over 80k dps now, with not too high HP as far as i remember. Haven't even done 1 lvl in paragon since i haven't played in ages.