I recently installed the U1 client for Mac (OS X 10.8.2). It's definitely got some rough edges, like occasionally taking forever to sync and the menubar helper doesn't quit when I select Quit. So I want to remove it completely. How do I do that?
We would love to have the opportunity to solve your problems with it - if you contact support at https://one.ubuntu.com/help/contact/ we will investigate.
In particular the menubar helper not quitting is a bug that I'd personally like to hear more about - if you have the time, a bug report that describes in more detail what you did and what the context was, and includes the log files from ~/Library/Caches/ubuntuone/ (those will contain file names, so you can mark it as private), would be really helpful - the place to file that bug would be here: https://bugs.launchpad.net/ubuntuone-control-panel/+filebug
If you would still rather completely remove the Mac client, here's how:
First quit the service (not just the control panel app) using the quit menu item in the menubar helper. (If that doesn't work, force quit everything with 'ubuntuone' in its name using Activity Monitor).
If you never run the app again, the ~/Ubuntu One/ folder is just another folder and nothing will change it.
You could stop here in case you would like to try using it again in the future.
To continue and really wipe everything: