I created subuser <subuser.org> which runs on top of Docker, and of course, packaging is as simple as it is with Docker... The big problem is that when you want to update something, it is hard to do so without making everyone have to download a huge image all over again. Of course, you can try to prevent this with layers, but usually updates don't just touch the top layer :( ... So what I really want in the future is to be able to use IPFS or some kind of bittorrent-like download interface for images, so that when you update an image, you only have to download the parts that changed. There is a GREAT demo by a guy named Mathias Buus on this very topic here https://www.youtube.com/watch?v=2Sc6_XgNXyk which really gives you a feel for the awsome that would be deduplicated content addressed Docker.

Flatpak has something sorta similar, they use OSTree under the hood. https://github.com/ostreedev/ostree which is basically git annex for people who like incompatible redhat/freedesktop specific implementations of generic algorithms. It also does dedup, but at the file level not the block level, and so flatpak should be better at handling updates than subuser/Docker. Then again, who wants to repackage everything with their weird "standard" overcomplicated image format when you can just use Docker and throw anything you like into the image, however you like to throw it....

They're a much easier way to package applications vs traditional packaging (ie apt, rpm).