you can get an overlapping sound effect from jump + trampoline bounce if the 1 second timer overlaps with the trampoline, I think that's unintended.
I don't have an incentive to get coins that require falling down, the price of having to climb back up is too steep to be worth it for me.
I stopped at the spiked boxes because I fell down, the spikes activated and they don't reset. I also think this mechanic might be too extreme even if they do reset because of the lack of player control over jumps but then I only attempted them once.