I just had a really frustrating situation happen.
I was being followed by 3 of those purple fliers, so I decided to see if the boomarang would save me. I made 3 attempts (3 seperate plots) and the boomarang each time flew out in comepletely useless directions, deftly avoiding all enemies on the screen each time. (The screen had more than just the 3 fliers).
Because I was giving the boomarang a fair shake, circumstances forced me against the wall with an overhang. Like this:
(Those plots were boomarang attempts)
Needless to say, I got hit. Problem was that I immediately went up against the ceiling, the game treated me as if I landed on the balance beam, and I was instantly hit a second time (this all happened at the same time). Sooooo I lost 2 hearts and somehow got out without losing a third. Very discouraging.
Don't quite know the solution, but this whole situation (from the boomarang being pretty useless and not acting in a predictable way to being hit twice for an inescapable situation) really took the wind out of my sails...