And that's why I said "apart for Linux". Where are the package maintainers on the OSes everyone uses ? (and don't think that's sarcasm, I'm writing this comment on my linux desktop).
My exact thought as well, simply point the user to a well established and proper channel for auto updates and then the dev simply needs to upload/release to said repos when a new version is put out. As an aside: Chocolatey is currently the only (stable/solid) way to consistently keep things up to date on the Win platform in my book.