Decent game. It has some really nice highlights: most notably the experience of the open world. The last two islands especially are well designed and I think the game did a wonderful job of immersing you and making you feel like Sonic.

The game starts off quite slow, but I think it really becomes fun after the second island. Just running around the world was something I got a lot of enjoyment out of. The controls are nothing to write home about, but they were pretty solid in my experience.

My main criticism would probably be the story, which felt kind of like an afterthought when compared to the world design. Another thing I was getting quite bored of near the end of the game was the overall gameplay loop: get gears, then keys, then emeralds, fight boss, next island. I wasn't minding it at first but some parts (especially the cyberspace levels - mostly just copies of old levels with very few design elements) can get extremely repetitive and tedious.

Overall, I think the game has a solid foundation for a sequel, a game I think I'll give a shot. I recommend the game, but I would only buy it on sale if possible. I got my copy for $30 USD and I think my money was well spent.