I know there was considerable discussion on IRC regarding the selection of emojis to use for the "love" and "hate" icons, but I don't recall the details.  The heart for "love" makes perfect sense, but I'm not sure that the broken heart is the best selection for "hate".  Perhaps a better choice would be the poop emoji.  The statement, "This song is a POS." is a much clearer indication that you hate it than, "This song breaks my heart."

If you want to avoid the poop emoji, then perhaps the "love" emoji could be a heart in a green circle, with the "hate" emoji being a heart in a red circle with a strikethrough (symbolizing "no love").  This format is pretty much universally understood, and would better indicate the two choices.