Here's the good and bad in no particular order. Feel free to ignore the bad you already know:
-unique walk, run, and jump animations for each character
-each character has a different stage/music
-Pinkie's wall-sliding animation is adorable!
-after I escaped the "course" on Rainbow Dash's level and fell off the bottom of the screen, I was returned to the start of the level. That may be obvious, but the levels appear to be designed in a way that isn't meant to include the traditional "bottomless pit," so it's good that it works anyway.
-I can't be sure because they're not on the same levels, but Dash seems to have the fastest, well, dash, in keeping with the show. Rarity doesn't like exercise and takes longest to reach full speed. Nice touch.
-There's to be a quick appearance of a jump sprite when you quickly switch directions walking sometimes
-rocks disappear in a very noticable way when they're half-off the screen
-rock physics - it's cool how they roll back and forth with a low center of gravity, but they roll more like balls with weights in them than lopsided boulders. One of the rocks in Rainbow Dash's level just kept rocking in place for minutes on end on its point without even being touched. Also, physics stops affecting the rocks after they leave the screen - Dash's falling boulders remained in mid air until I saw them again.
-as pegasi, bumping into the underside of something or walking off an edge without jumping stops you from being able to fly until you hit the ground again
-the wing-flapping animation for the pegasi doesn't play if you hit spacebar too fast
-landing on the very edge of a block, the game starts switching really fast between a falling sprite and a standing sprite
-as Fluttershy, when I was flying from right to left, she would sometimes jerk around at the top of each "flap" like she was starting a different animation suddenly
-if you use magic on a rock, then move the mouse off the rock while holding down the mouse button, it still moves the rock like you were clicking on it.
-The magic skill is odd - you can't control the direction or speed things move, you can only make them move faster from right to left
-Add more idle animations - maybe just some continuous breathing or something in addition to their current ones. Also, maybe longer "long-wait" ones, or multiple "long-wait" ones that cycle as you go through them.
-Pinkie and AJ are the only ones with idle animation
-Have a transition frame when the character lands from a jump
-change Applejack's wall-sliding animation - it looks more like she's sinking through the wall than sliding down it
-consider another way to use magic - switching between the keyboard and mouse in these things always feels a little awkward
-there doesn't seem to be a "ceiling" to Fluttershy's level - once she flew high enough to go off the top of the screen, I tried flying continuously for different amounts of time and then seeing how long it took her to fall back down - it was always a greater amount every time I spent longer going up. I don't know if this applies to the other levels, or even if it was done on purpose or not, but unless they need to go offscreen, like in the original Super Mario Bros. for example, maybe stop the player from being able to go off the sides and top of the level.
-for their running animations, the ponies start off with their manes and tails flying straight out like they're at full speed, even though they obviously build up momentum over time - give them animations to match their current speed.
-be careful with pegasus levels - flying and platforming don't always work together
-more kinds of obstacles, and maybe some enemies.
-again, don't know if it was on purpose, but Mayor Mare isn't gray.
Overall, you have the makings of something good here, and you're off to a great start. You need to tighten up the controls, improve the animations, and pay attention to ALL of the little details - it seems odd when you pay attention to some things but not others
ONLY REAL MEN WATCH MY LITTLE PONY WELL, IF A MAN COUNTS AS A 16 WHO LIVES IN THERE PARENTS BASEMENT
Huzzah!!! the fun will soon be doubled!!!!!!!!!!!!!!!!!!!!!! *yay*
awesome job man but it still need a lot of work i just know once it's all done it's going to be...
PS. and the fun will be doubled lol