A different kind of 2-D Sonic. Still the same fun.
The quality of the game is also very high. The graphics are very nice, the music will pump you up to no end, and the voice work is actually tolerable.
What hold this game back from being a must have is some of the level design. Going fast is ok, if obstacles didn't come up at the most inconvenient times. Some times an enemy will come up getting right of a spring, not even giving you enough time to curl into a ball or using the boost. Trial and error is one thing (cmon, all Sonic games have it), but sometimes I feel they get carried away.
Still, take the game's difficulty for what it is, because a lot of it is intentional. Take the special stages for example, they're NOT easy. This definitely takes the old design philosophy of the old Sonic games, and amplifies it, to the point where its a whole different animal. Maybe it's more of an action game than a platformer now, but it's still a lot of fun, and still keeps that same tone in gameplay.
Overall, its a worthy addition to the Sonic franchise (thank you Dimps), but should not be compared to it's genesis/mega drive counter parts, like Sonic Advanced.