After getting all achievements and challenge times, I can confidently write my review about the game.
I'm not usually a fan of speedrunning, but every now and then, I enjoy casually playing tailor-made experiences like this one.

This is a speedrunner game, there is no point in playing if not for speedrunning, so be aware of that before you buy, not only is speedrunning the main goal, but also the expected out of the player. If you can't clear at good times, you do not unlock later stages.

There are some games that try too hard at demmanding the best out of the player and become really tiring to me, but this one has a nice balance of demmanding just enough so that you don't auto-beat any challenge, but you are also not exhausted by having to try too much. If you ARE into hardcore speedrunning, however, by all means go ahead and enjoy yourself at the leaderboards, you'll have a pretty good time.

The platforming is smooth and the game has few, but very well implemented and creative mechanics.
Graphics are cool, it plays really well, you really feel in a trance of flow and speed.

I'd say the challenges come in 2 flavors, the initial stage and final stage that speedrunning has on any game:

The first stage is when the challenge itself is not that difficult, but possibilities are plenty, so the goal is to figure out the optimal way of getting the best time by being creative and precise.
The second stage are the in-game challenge modes, where you're gradually introduced restrictions to the stage (in the form of specific paths, extra hazards and extra targets) that force you to find the best way to complete a specific, challenging and tight route, specially when all of the restrictions come together in the final challenge of each level.
Both stages are their own kind of experience and both really deliver at what they set out to do.

As much as I enjoyed the soundtrack, I don't think it is varied enough for how much you'll be replaying each stage, so that bothered me a bit after a few hours in, with that said, the game does not overstay its welcome, so that isn't a very huge problem.
I also have some nitpicks with menu navigation, but they are extremely minor issues.

The game was well worth my time and money, I certainly recommend it if anything I said above is to your liking.