Well, today was something. I downloaded a nightly Firefox build and decided to see about breaking the Extensions Manager. So I went to update.mozilla.org and found a few of my favorite extensions: Gmail Notifier, Checky, LiveHTTPHeaders, Web Developer, User Agent Switcher, among others.
Installed them all (at once), then quit Firefox. Restarted Firefox. All worked perfectly. Checked for updates, no updates found. Everything worked without a hitch.
This was the first time it’s been a good experience with the feature for me. And this time, it was flawless.
So hats off to the dev’s for a quality job. The move towards 1.0 is a looking good.