It feels good to be vindicated. I watched the "making of" video in the game's bonus features, and the creators pretty much came out and directly confirmed the theory in my first post - Jet Set Radio was made by taking a lot of popular trends and just building a game around them. The result wasn't always the most coherent thing in the world, but it did have a certain amount of earnest charm.
I probably shouldn't have played it much past 10 hours, though. Once I finished the story missions, the only thing left to do was attempt the game's various challenge modes in an attempt to maximize my score. And while it was nice being able to explore the levels without being shot at by goons the entire time, I could never quite figure out the game's stunt system, and thus my point scores remained dismally low.
Overall, it wasn't a bad way to kill time, but I never really felt that fire for mastery that inspires a great performance. I wasn't really trying to get better. My goal was always to be moderately diverted until my time ran out. I mostly succeeded at that goal, though perhaps, in the process, I did not give Jet Set Radio the respect it deserved.
I don't think I'll play this game any more, though. I still have a long way to go before I hit the ceiling for mastery, but that's not the sort of challenge that appeals to me. It's all about precision, timing, and well-honed reflexes. Impressive, if you can do it, but frustrating if you can't. And I have little desire to push my way through the frustration just for some nebulous bragging rights.
That said, I did enjoy the game. I'm glad I played it. I liked its goofy, colorful world and rocking soundtrack. I liked unlocking new characters with a variety of bold 90s styles, but would have liked it even more if they had deeper characterization and individual side-stories. If they ever release the sequel on PC, I will definitely consider picking it up.