The chromium project releases their updates for Ubuntu users thru a PPA, but Canonical also distributes stable packages. A mix that is working really well.

God forbid #2, a system-wide system for downloading and updating applications is one of the zen-things about using the Linux-based OS's.

How it works on Mac OS X and is chaotical, and the way Microsoft does it, with countless messy installers and self-updating apps is hell to deal with.