I would assume most of Dropbox's appeal lies in its cross-platform nature, but for me that's turned out to not add much actual value. I find that I don't really need everything to be everywhere and accessible at all times… no point in most of the things on my daily driver Mac to be accessible from from my gaming desktop or ultrabook used mostly for studying.

On the odd occasion I need something to be mobile-accessible, iCloud does the trick (and if I were to switch to Android, Google Drive would fill that niche). Once a blue moon when I need to get files to other machines on my local network, Syncthing and Snapdrop do the trick.