I finished Skies of Arcadia in about 45 hours. It was very enjoyable time spent. I thought the story was well done and didn't require too much heavy thought.
The battle system is well done and very original, unfortunately, it is not necessary to use magic spells to complete the game. They are quickly made useless with items or the more powerful character specific "S-Moves".
The battles did not seem very memorable either. The primary battles were slightly challenging, while the end battles took no skill to beat. This is not a very difficult RPG in any way.
While it is not difficult, like I said bofore, it is still fun. I didn't grow bored of the characters or the game. Random battles are frequenct, but they are over fast enough that I was not distrubd by them.