As someone from the affiliate space where EVERYTHING gets splittested I can tell you that videos generally own all other forms of website content when trying to get the user to do something (download, signup, buy).

>Would Dropbox convert better if they had descriptive text on their home page, or at least made the features link more visible than the one in the footer? We'll never know unless Dropbox tests it and publishes the results.

of course DB tested their homepage a ton