Pretty great classic experience, for the positive I'd say the way u unlock new abilities in this game is very well done, the levels are challenging and colorful, the robot masters are decently challenging but not absurd either without weakness. And also the way they handled the use of the 2 characters was very well done, it's pretty annoying when you have to go through 2 different campaigns just to play as the other character.
On the negative side, I think the game overstayed its welcome with over 6 wily stages... And I also believe rock's perk is way better than roll's. Charged shots come in handy in many situations and I don't think the double jump makes up for this disparity in power.
But still, the game was pretty solid and I will prolly come back to it as much as the official games in the future.