Sonic Heroes looks good. That is about all that can be said about it. The levels are huge but nothing to amazing. The game sounds very clear but the music is pretty lame. It could have used more polish in those areas.
The gameplay sounds neat, but for the most part it really isn't. The 3 characters per team makes everything more complicated then interesting. Sonic is fun to use, but I didn't like any of the other characters. The battles are really slow and choppy. The level designs aren't the best either.
The game does offer a bit of replay. There are 4 teams to play with (all characters from Sonic games) but most of the levels are just variations of the others. The multiplayer mode isn't really fun so don't expect to get much replay value with that.
Final words: While this is a good game, it doesn't live up to the past Sonic games.