Pros: Pretty good tonal balance overall for its price
Cons: Not very comfortable, a bit too bright, looks like its price bracket
I needed decent closed-back headphones for tracking, and while the Audio-Technica ATH-M50 is a much better pair of headphones overall at just $50 more, the Equation RP-21 is actually not bad at all for sub-$100. The tonal balance is quite good and does not exhibit any glaring problems like bloated bass or rolled-off treble or other similar problems we often hear in budget headphones. The upper mids are a bit bright though, and while it's not nearly as bad as some other headphones, for people who really like a non-fatiguing sound, it's a bit brighter than ideal. The sub-bass extension isn't anything special--it's about average for full-sized headphones, but the overall weight and accuracy of the bass is better than a lot of headphones in its price range.
Comfort-wise, it's just tolerable--it doesn't sit too comfortably on the head, and the way the earcups sit around the ear feels a bit strange--like it wasn't properly molded to the human facial contour. But it's not painful or uncomfortable though--just something you will notice on your head, as opposed to forgetting they are there with really comfortable headphones.
Looks-wise, it looks like a sub-$100 pair of headphones, but the color choices and the design is fairly easy on the eyes.