Rated 4 out of 5 stars
A few suggestions for the Perspectives add-on for Firefox :
1.) allow the status bar text to be enabled/disabled from within the extension options (this limitation can be manually worked around by installing another extension called 'Organize Status Bar')
2.) have an optional alternative status bar item that is more compact than the existing text 'Perspectives'. This might be a gray version of the green checkmark icon or a 'P' or something else. Maybe a gray P that is replaced by a green checkmark when verified by Perspectives. Just something that doesn't use so much status bar space when enabled. Maybe the https lock item can be changed to show 3 states (verified by cert auth, verified by peers or notary over time, unverified).
3.) offline cert cache of visited sites to limit number of needed queries to notaries (cache should be clearable with the Firefox Tools menu Clear Private Data option)
4.) option to automatically allow secure connections to any IP in the private IP address ranges (e.g. 10.x.x.x, 172.16.x.x 192.168.x.x) (a more restrictive option would be to allow these connections to machines in the same subnet as the PC running the browser)
5.) take a look at the WOT (Web of Trust) add-on...there may be value integrating the add-ons/features to make safer browsing decisions