Their UI is much better than their competitors, and they have some great major and minor features being released that others don't have, and they charge the standard set by their competitors.

Sure, compared to buying a physical drive it is expensive, or compared to setting up your own VPS, but there are clear downsides to those options.

I recently looked into moving form our current (really shitty yet fascinatingly expensive) cloud storage solution, and even though I still have a grudge against them for shutting down Mailbox...Dropbox was by far the best solution for us.