First of all I'll say that I liked this a whole lot. Gameplay ties well with music and for the most part it looks great. Vinyl's sections are particularly clear and pretty. Controls feel pretty good and responsive (for a one button game, that is) and it's a great way to spend ~30 minutes, varying greatly depending on player's experience with similar titles. Overall grade would be something like 8+/10.
That said, I have two issues with it.
First of all, I absolutely hate color scheme used in Derpy levels. Obstacles aren't immediately obvious and the red patches in background can easily be confused with terrain. Doubly so because similar patches are used in Octavia's levels to show you where to jump next. Yellow doesn't really work there and in some sections leads to even more visual clutter on screen.
Secondly, changing how particular pony moves during her section should be displayed on a screen in some way to prevent "unavoidable" deaths. To add to this, the Vinyl segment shown in second screenshot, especially jumping down at the correct time, is more precise than any other part of the game. It's fine to have some harder sections in an otherwise not too hard game but I'd either move it closer to the end or make it couple pixels easier.
Also at least for me there's no "THE END" screen, Octavia just continues to forever run out of screen.