I have played Perfect World, It isn't really a big deal, It's a little cool at the beginning while you unlock abilities, get some cool looking armour and gather nice things that give you some sense of achievement, but then you realize that all the quest are exactly the same "Kill X number of monsters" "Gather X number of things killing Z monster" (Is only a more annoying version of the former) "Go talk to this 4 NPCs, each one is at different corner of the world" or "Gather X material" It goes like that until you get to level 30, then you get to fight bosses, which only are super mooks that need to be taken down in group, now that I think of it Perfect World is incredibly similar to WoW, so if you like that kind of game play you will love it.
I agree with snalin in that D&D online is a great MMORPGs, why? Questing is amazing! You don't get that "Kill 10 rats" crap, each quest is unique, with an unique dungeon, story, objectives, the narrator really helps the atmosphere and you really feel the need to have a varied party, Mechanical traps can only be disabled by thieves, magic barriers can only be disabled by mages, clerics are the only ones who can cure fast and effectively, Rangers can decimate groups of enemies before having to engage in close combat, Warriors . . . they are strong and Bards can give nice buffs to the party, granted, every quest can be completed alone but you would miss tons of loot, it would be 10 times more difficult and I gotta say that it is really nerve-wracking to complete the longest dungeons by yourself, the potions are never enough, your weapons seem to broke on the most inopportune moment and you never know what enemy or trap lies beyond the next door or if you will be able to handle it.
Yep, really worth a try.