I'm used to tabbing through Bugzilla, despite the number of fields it has (so I get annoyed whenever you e.g. add another link to the create attachment page.) However, when I got to the new Keywords field, I got stuck. Initally I hoped that hitting Tab enough times would dismiss the popup when I reached the next real field, but eventually I worked out that once I'd tabbed to Cancel I could hit space to dismiss the popup, but focus was by then completely lost. This bug wouldn't be so bad if I could turn off that popup.
This is basically a duplicate of bug 452734, because fixing that will probably fix this.