zero useful. You really want to set the tags, description, title, and all the other setting before you click publish. otherwise it will publish a video with no seo. you can add that afterwards but thats not great as it takes a while to get reindexed for search i think. It would a good idea for non branded personal channels for people that don't care about above
I like to use dropbox to share files, but I don't think I'd upload finished YouTube videos from Dropbox unless there was a super easy text file format I could use that would fill out the description / tags / titles / thumbnail / etc. in one file. That would be convenient because YouTube's video management forms are kind of annoying.