Most of the functionality seems broken in Firefox. Chrome plugin is fine (generally works, though UI has some issues) but the Firefox addon seems to have relatively few actually working features. A preview of things that are broken (not exhaustive):
1. Can't unlock accounts that are set to "required password re-prompt"
2. Can't add sites.
3. Can't copy password from addon.
4. Search box isn't default selection for typing when opening the addon.
5. ctrl-c in generate password box doesn't copy the password, it just appends the letter C to the text field. You have to right-click copy.