I bought the game a few days after it released. I'd followed the game's progress loosely, and never donated to the kickstarter. But when I did get my hands on the game, I was taken aback by how wonderful it was.
First off, most of the Sonic comparisons are unfounded. There are definitely elements that remind you that this used to be a Sonic fan game (did anyone else notice that the main villain has Robotnik/Eggman's mustache as his eyebrows?), but the gameplay has far more similarities to the Rocket Knight series, with a bit of Mega Man Zero, Gunstar Heroes, and Chip & Dale Rescue Rangers flavors added for extra zest.
The game is also very lengthy. I've beaten the game with all three playable characters, and it took me about 16 hours. Granted, since I bought the game early on, I had to deal with the pre-nerf versions of the Final Dreadnaut bosses, which ate up a lot of game time due to their high difficulty. The game is quite lengthy, and with three highly unique characters to play as, you'll definitely get your 15 dollars worth. Not to mention we'll be getting two free DLC characters somewhere along the line, which will increase replay value even further.
The jumping physics could be a bit better, and I have run into at least one game breaking bug (which I believe has been patched out as of yesterday), but the only large problem I have with the game is its story. The characters are all interesting enough, but the story tends to meander around and generally waste your time. Events could be much clearer, the world could be expanded upon, and transitions made much smoother. There was also a bit near the end that was such a flagrant ripoff of Cave Story that I couldn't feel an emotional reaction at all.
Having said that, I didn't really go into this game expecting it to have lengthy cutscenes at all, and I suppose it's a good bonus that the team at least tried. Plus, the game offers a handy Classic mode that takes out all the cutscenes (except very minor ones, which play out silently as in Sonic 3), and simply lets you play through the game level-by-level.
Overall, I am extremely pleased with this game, and thanks to the hard-working dev team, it is getting better by the week thanks to patches.