General

It's the only reason I'm back to playing this for a little while. The best part is that [b]they don't need mastery books![/b] I hate merching and so I generally have to stop most of my characters at 100-120 because I can't afford the skill books. The CK expansion is great, if only for that reason.

I've tried out two:
Wind Archer (mine was already 120): It seems pretty powerful to me. I have crap for equipment, but it's still hitting like 300k (total; about 60-80k per line) with that wind-pierce looking thing. Sharp Eyes for free, and no need for Maple Warrior. It's great. Lots of mobility, too. It's not as powerful as my Demon Avenger, but my Demon Avenger actually has equips (that still suck, but whatever).

Thunder Breaker: I had one on another account, but that got banned, so I have a new one. I've played it to 38 so far. TB has a LOT of mobile attacking. Basically you can chain together the teleport attack with roughly anything, and then chain that thing with anything. You'll need some fast reflexes to take it to its full potential, but the new TB, from my experience, utterly clears out maps. The layout doesn't even matter, he just teleports to enemies. Makes me remember my (... now banned) Hayato, and how it flew around the map.

Haven't tried DW yet.

Dawn warriors are okay as well, first job has a 1 hit mobbing move.
2nd job has two moves that can chain onto the first job mobbing move, it's pretty sweet.
TB's are enjoyable to me, even though they only have a simple 1 step chain for first job.
I can't enjoy WA cause first job is still one skill

Wind archer is OP
Thunder Breaker combo chain is fun
Soul Master haven't tried

Yes they're quite enjoyable. I couldn't be bothered continuing my Thunder Breaker though since I had no idea how the combos worked and I have him absolutely naked.
But yeah they're all pretty fun.