Are you using the Personas extension or just the inbuilt Personas support? I myself am using the extension (although an older version) and I don't need to log in (after I logged in the first time) to use my favorites... Are you sure you're doing everything right?
I believe that it's the extensions. If I don't log-in every time I start FireFox, the rotator brings up the last persona that was on my browser when I last shut FireFox down. I'd like the developers to creat an option under TOOLS in which a user can select autoloading of the persona favorites versus having to log-in everytime FireFox is started. Rotating personas every minute is a great feature, it's just a little ackward still.
I agree, they need to have an option to make personas rotator start as soon as you log in to Firefox. I hate having to leave the screen I'm on, just to lot in to that preferences page, then I close it again, anyway.