Private repo with public downloads
Just like private repositories can have public issues and/or a public wiki, it would be cool to have that option for downloads, too. That way, I can start a project in private, offer people downloads, and open it up completely at some point.
I'm interested in this for my research code, which I want to keep private until it's published, and then flick a switch to make it open source. During reviews, it's still nice to be able to point people to a place where they can download the program from a neutral party (i.e., not my own website where I could track who's reviewing).