The success of Phantasy Star 0 is largely dependent on how you play the game. If you prefer to play games like this by yourself, then it's probably best to steer clear of Phantasy Star 0. The mechanics haven't aged well, and there are far better games out there deserving of your hard-earned cash. If you happen to have friends who are eager to play with you and don't mind overcoming the hassle of online play, there's a surprising amount of fun to be had with the game.
Whichever camp you find yourself in, Phantasy Star 0 doesn't quite live up to the memory of Phantasy Star Online from 2000, which if nothing else, highlights just how far the genre has come in the last ten years.