As a critic, I don't like to admit that I'm wrong but I can, and do. Still, that doesn't mean I like it. Naturally, I try to be wrong as little as possible—but today, I need to 'fess up big-time. See, I used to think Billy Hatcher and the Giant Egg was a bad Sega game, but that was only until I played Sonic Heroes. Now, I see lil' Billy as a virtual masterpiece by comparison, practically the digital equivalent of a Guernica, or Starry Night. Why? Because Sonic Heroes has so much wrong with it, that three lefts couldn't make it right.
I think they started off on the right track, and the use of "team" is a great concept. But, I'm going to have to disagree with Jason and say that the implementation just doesn't work. In essence, the level designs aren't conducive to using all three character styles effectively. Since Sonic's speed clearly overshadows the rest of the trio, every time you actually need to use strength or flight, it feels like the game stumbles over an unwanted speedbump. More annoying than justified and valuable, the three-way mechanic seems highly unbalanced, and not very well thought-out.
The levels are also far too lengthy, as Jason mentioned. I consistently found that there was plenty of road left to travel after the novelty of each area had long worn off. Besides that, the patented Sega "BrokenCam" (originally debuting on the Dreamcast) is still with us today, showing that even after Billy and the other Sonic platformers, it's still impervious to any repairs no matter how badly needed.
Sonic Heroes looks like a good thing on paper. It's a fresh concept and seems like it should work, especially given the characters involved. However, the fact is that Sega still hasn't managed to polish their 3D skills to an acceptable level despite several disappointing attempts. If you really need a Sonic fix, pick up the GameCube's Mega Collection instead.