These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Earworm: The stage select jingle is pretty well received.
Guide Dang It: Getting some of the hidden pokemon to appear (or evolve from pokemon on the stage) requires either knowledge of the Pokedex or a walkthrough.
It's Short, so It Sucks : The main game can be beaten in a couple hours. 100% Completion doesn't take much longer. Gets flak for this. The current non-100% speedrun of the game clocks in at 22 minutes and 55 seconds. 100% one clocks at 26 minutes and 8 seconds. See them here.