These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Anti-Climax Boss: Metal Sonic Kai. He may be big and intimidating, but he is just way too easy for a final boss—the only danger in this boss is getting smacked during the second phase, which is still not much of a problem, and otherwise he just floats around and launches attacks that are ridiculously easy to dodge, while you pummel him to pieces by either spin attacking him or throwing your buddy at him.
Awesome Art: The game really took advantage of the substantially larger color palette, sprite scaling and 3D effects of the 32X, resulting in a Genesis style Sonic game with substantially souped up art. The special stages and one of the bosses are even done using real-time 3D!
So Okay, It's Average: The general consensus of the game is that, while cosmetically lush and having potential in it's array of characters and gimmicks, it is let down by bland level design and clunky physics.