Hi DavidR,
Even with Nightly Tester Tools your add-ons/extensions just will be checked for newer/latest versions, you always will have the latest versions of the extensions inside your Mozilla browser and as developers of mentioned extensions want their creations to work in the latest nightly build and beyond they will run there or it means the extension developers just hold the line. I know whatever Firefox (pre-)(beta-)build NoScript always runs there and that is enough to be protected from yesterdays threats, today's threats and threats that even have to be dreamt up in the near and/or faraway future, so I have full confidence in my flaw of browser, a thing I cannot say when I am on not so familiar ground with STWare's Iron, GoogleChrome or IE8 even. I just wanted you to know that and I experimented around with my Firefox browser with all sorts of chrome and content files, fuzzing all sorts, analyzing error consoles, firebug reports, testing Mozilla bug patches and the outcome of regressions, know some great coders out in the trenches where firefox wants to go security wise and like the versatility. What I lack is the sandbox features like GoogleChrome brought them in, but you cannot build firefox up from scratch like the developers of the Google browser did, and mind you folks, this is an awefully secure browser as well - the hackers could not get a dent in there, mind you - that has been proven. Then also don't forget we have the webshield to protect us, and avast there is "state of the art". I learned an awful lot being a Firefox nightly build test pilot, but I can also understand those that do not have the guts to follow where I venture out, and even I will never take even a calculated risk, visors up, always!
polonus aka luntrus