I had it pre-ordered it since I played the demo in MK: DD.
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Now that I am finished with the story modes, I can say that this an overall solid game.
It is more closer to the older Sonic games (Genesis) than the Adventure games are.
The only problem, which can actually be a good thing, is that the levels are pretty big. Some lasting more than 10 minutes. The team aspect of the game seems to work out quite well, but it might get a little annoying switching to Tails to fly over a gap, when you are blazing quickly past the level with Sonic.
The camera is still a bit .. iffy xD. They have improved the camera since Sonic Adventure 2, but sometimes... it can be a pain. Good thing is you can switch around the camera while moving and set it like that.
Also, the emblems are back! Every time you collect 20 of them , you get another 2P mode. Some are pretty useless IMO.
Overall, I find this a very good game, and I'm going to play it until I get all emblems and A ranks. If I were to rate it on a 10 point scale, I would have to give it a 8.5/10