It supports multiple platforms (web, android, ios). But the best thing about Papers is the annotations you can do on your papers. I like to annotate mypapers a lot and you can easily do annotations and review your highlights.

I used Papers 3 (legacy) a mac application during my PhD which was already awesome. the New Papers app is even better because of its multi platform support. Review collected by and hosted on G2.com.

Papers is best when you have a pdf of the paper. When you don't have the pdf, i sometimes find it bit hard to extract references as it lacks copy past (bibtex) based import. Review collected by and hosted on G2.com.