Played it earlier and it was good, but do you really feel the player should spend so much time riding a line platform to a dead end just to get a mushroom in the beginning? It was such a tedious process that on subsequent tries I just went straight for the ON/OFF switch and played the level small. Made things a bit more challenging, but I would rather take that over the forced wait for a powerup
I also never found a midway point either, which wouldn't be so bad if the stage weren't so long and lacking in powerups... and time (I ended the level with only 40 seconds remaining). If there was one and I completely missed it, maybe you should consider relocating it.
Otherwise, a fine level.