Another problem I found with picking a vanity url for my public CV on Careers: the auto-save always moves the cursor to the end of the line. This makes it very disruptive to change the url. Say I used "jdoe" and wanted to change it to "johndoe". I might end up with "jodoehn" or "johdoen", depending on how quickly I can type.
Minor, doesn't happen in Firefox 3.5 (though I can repro it in Chrome), and should be resolved by the other request you made.