I liked this a lot! The controls are nice and snappy, and the rot, wall climb, and double jump mechanics work well together.
However, I think the slow scrolling makes the game worse, since it works against the core of what the rot mechanic is about -- keeping the player moving. But because you can't go up faster than the screen, I spent a lot of time just waiting for it to move up (in many places, it was only possible because the rot mechanic seemed to be a bit buggy, as in certain instances, I could stand on a cloud without rotting it). The slow move to make you continue up is fine (but probably unnecessary), but I'd have liked the ability to push the camera up if I get to the top. Or just have the screen move be a bit faster.
But other than that, I was really impressed, and enjoyed it a lot!