Honestly, Unleashed was pretty bad. Sonic was a slippery shit to control and I thought the level design for the day stages became rather hellish about 2/3's the way through the game. I still can't fathom why they would map the homing attack to the boost button and then add an air boost on top of it (granted the homing attack is much more reliable in this game than in previous Sonic games, but it still caused me a bit of frustration whenever Sonic decided he didn't want to lock-on to an enemy and boosted himself into oblivion). The pacing of the game was absolutely fucked because of mandatory medal collection (because the first thing you want to do in the fast daytime stages is slow down and look for medals).
And then you have the Werehog. It's functional and that's about the best I can say about it. The enemies don't challenge your combat capabilities in any significant way, the puzzles are embarrassingly simple, and the platforming is as boring and bare bones as it gets. And then there's that battle theme that interrupts the night stage's pretty awesome music almost every time you get into a fight. Also, the Werehog takes up so much of the game's overall playtime, it's ridiculous, and it gets even worse when you have to back to look for medals.
The story was rather drab for me too. I don't care much for the bigger stories like this game and the Adventures had. I always thought Sonic stories work better as when they're a smaller, like a Saturday morning cartoon kind of thing (I thought stories like Colors and Lost World worked rather well even if Lost World needed a bit more worldbuilding for the Lost Hex). I also didn't care much for Sonic and Chip's relationship throughout the game (I thought Chip was a rather boring character all together honestly). The best parts was whenever Eggman showed up, and that's mostly because Pollock's performance as Eggman is absolutely superb 100% of the time.
Sonic Team had ambition, and you can really tell that they tried their damnedest with this game, but I really don't think it worked out in the end. The best thing that did happen is that they took what worked from this game and moved on to make Colors and Generations, rather than just scrapping it entirely like they usually do, and I certainly appreciate it for that.
If you're going to get the game, at least do what a few of the others here suggested and get a save file with mostly everything completed (I wasn't even aware that you could do that, huh). There's some fun to be had with the day stages, but the game really doesn't work as a whole.
