According to the release notes of Firefox 18.104.22.168, the edition issued Tuesday, the browser hasn't yet been given the all-clear for Vista. Among problems still on the list: Firefox cannot be set as the default browser in Vista, and updates may fail if the application is installed to a directory other than the default.
A total of 34 Firefox bugs related to Windows Vista have been collected in the Mozilla Bugzilla database; 20 of the bugs remain unfixed. Several relate to Vista's new parental control features that let families lock down or restrict access to the Internet.
Some of the bugs also affect other Mozilla products, including Thunderbird. For example, Thunderbird isn't able to act as Vista's default e-mail client.
In August, Mozilla developers accepted an invitation to use Microsoft's open-source lab and hobnob with Vista engineers in order to prep Firefox and other programs for the upcoming OS.