Karos is pretty fun. The dungeon system is pretty cool too. They just had a couple expansion granting more PvP and gunner class. The fletta system can be pretty rewarding too, enhancing attack speed/power/etc (it's up to you) or simply use it for crafting. Grind isn't that bad, and there are normal and repeatable quests. The community is active and friendly and graphics are pretty dang good with gorgeus cities. It's worth a shot.
edit: Forgot to mention that combat can be quite slow at first, but when you level up further it speeds up quite a bit.
I personally didn't like Karos very much, although it may be that I just didn't give it enough of a chance. I played a Sorceress/Banshee (the debuffer basically) and was disappointed. Pretty much all of the debuffs had long cooldowns and were single-target, which seemed a bit ridiculous in a game where party-play (from what I had seen of it) seemed to consist of fighting multiple smaller enemies more often than fighting single larger enemies. If I recall correctly, I began just ignoring my debuffs in most fights and using my attack skills because that seemed more effective overall (sorry, I can't comment on blader since I never tried it)
I wouldn't call Aika a 'great' game, but it's at the very least better than Karos in my opinion.
you cant even remap keys in karos, and gameguard prevent using key remapper software.
its incredible games cant remap keys in 2010. stupid korean piece of turd.