I've looked for Dropbox alternatives, and none of them match up in ease of use or features. A folder you put stuff into and that syncs to everything else (with optional selectivity so that your 250 GB music library isn't synced where you don't want it) is amazing, and that it works on everything from iOS to Windows to Linux is amazing.

It'd be great if the clients were native and faster or whatever, but shipping beats perfection.