I quit on the side scrolling part with sticky keys (My reflexes can't handle it, too much. I was about to quit on that godawful 1st room of the castle.). I love it. I'll be playing the final version. I'll give my opinions on each part.
I liked the place where you must platform to get to a new game. This further discourages me from playing anything above medium, lol.
The start of the game is nice. The tree stump thing made me lol.
The Trails thing is a big "fuck you", IMO. I tried it like an hour ago, I quit. The moving platforms look easy, but in reality they are awful. I can't get all of them, I had 9 to go and was killed by sand.
The plants shooting fire that homes in on you is frustrating for a bit. The chest shooting coins was easy. The fire destroying platforms part made me think I just had to run fast until I accidentally pressed the left key at the start of the room. Cacodemon pissed me off.
I hate the area after Cacodemon. All of it: Both upper and lower paths.
The wrecking ball made me go "WHAT THE HELL?!?!?!?!", I didn't expect it. The area after that was amusing, I like how the plane comes out followed by a bombing. The portal area was genius, though I wish you would have added a save point after the turrets or whatever they're called. Block jumping was fun, Underwater wasn't that fun. Bub looked freaking impossible after everything was shooting at you, but I beat him. The rest of the underwater area was fine. I didn't care for the area where there are two kids, and the room where the 4 plants are shooting at you really ticked me off. The Pac-Man area was fun, the pokemon area was win, the battle was EPIC win, but,then came the lower half of the underground area. I didn't like that. The part with the X's I hate so much i wished for it to be removed are improved. Also, have you taken out the "No Bow" areas? That ticked me off on the race segment that i couldn't go through. Anyway, the 1st room of the palace was hard, and II quit on the scrolling room.