Rated 4 out of 5 stars
Well I don't have multiple popups for master password, but I tried this out anyway and I like the feature where the main window is hidden.
However... the extension pentadactyl offers two ways of quitting firefox. If I quit using the ZZ shortcut, it turns on the "show my tabs from last time" setting before closing firefox, then the next time firefox starts, the setting is returned to "show homepage".
Somehow, StartupMaster is interfering with this, and my session is not being restored. I tried ticking the setting about loading extensions at a different point, but it didn't solve the issue.