First , i wanted to mention that this game is no much of Sonic as many write. Yeah, certainly there is some bits and ideas was taken from Sonic, but not that much. Moreover, i kinda fell it more similar to Bubsy then Sonic if you dont want to play it fast. Once you go to explore levels you quicly find a lot of various path, caves, treasures and stuff. Even more, there is "vertical layers" and no main road allowing you to complete level several time with new experience each time. Not often you see game designed this way.
As for gameplay itself its mix of platforming, charming story, supercute characters, lot of nice jokes and, somewhat, challenging fights with bosses.
Game becomes quite hard pretty quickly and even with a lot of health and plenty of heath powerups you will find yourself sweating a lot. Some levels little too much hectic and action intensive for me. Thanks game dont make you to repeat whole level in case of death at boss fight.
Graphically there is nothing to whine about. Its colorful, its bright, not to excess, its "16-bit", but not in hardcore way. Maybe there is little lack of attention to details at some levels, but i guess its fine anyway.
Music is pretty good. Cannot call it superb, i heard better soundtracks, but it fits game pretty well.
Story getting somewhat awkward at some points, but i like its lighthearted atmosphere .
As for replay value there is several characters to play (so far i prefer Carol, cause i found here easier to control) with with different abilities which can change gameplay style a lot. Also "alternative paths" mentioned above will add exploration interest too.
So, in conclusion i recommend this game for everyone. Maybe its not will be everyone's favorite but i dont see how can someone dislike it.