The few extras aren't worth it imo, even back in the PS2 days.
A few mystic artes you'll never see outside of the end of the game and a few silly costumes isn't much to care about if you have the original GC version. I say the most interesting addition are the Unison Attacks since they're pretty badly distributed, and the PS2 exclusive ones give a few more to Sheena, Regal, and Presea at least.
It's playable, but it's just badly incompetent for Namco to release it in this state. I wouldn't suggest this HD port to anybody but a hardcore Tales of Symphonia fan (which means I'll get it since I'm used to the PS2 version despite my complaints) since the GC version is superior in performance.