I like it mainly because of the fact that you don't have to download anything (*cough*700mb file in particular*cough*) ;;;
The game in general... is a little laggy during peak hours, yeah. It's probably an issue for some users too because of the Adobe Flash Player memory leak issue, but when I play during my time (non-peak hours, normally 150~200 players online per server) it's pretty much smooth for me. <3 But yes, there're several areas they could work on to further improve the game, and like any other MMO, it's bound to lag on a PC that can't handle the load.
If you're not involved in Minishops or the Exchange, it's a pretty good way to earn money quick too (IMO) - getting rings, farm orbs, charging them and reselling for high prices. *Q*
Love my Shark Attack/Shuriken/Fire Rain ;_; crazy damage much~