For Firebug 1.4 we want to try yet again to improve the enabled-panels user experience. The 1.2/1.3 solution is too complex for users and too hard for us to maintain.
One idea is to turn on the resource-hungry features only for web pages that Firebug is open on. If you are debugging, you have your site selected and you have Firebug on. If you wander off an read your email, you don’t have Firebug up. Firebug would be on when you are debugging and off when not. Makes a lot of sense (even if it is not as easy to implement as it sounds).
Part of implementing this is to remember what pages you had Firebug open on. And one way to implement this remembering thing is the Firefox Places tagging API. By tagging pages as “firebugged” when you open Firebug on them, we can check this tag when you open that URL later. Maybe you don’t like us to mess with your tags, I don’t know. As part of the trade off, you can type ‘firebugged’ in to the location bar and get a list of all pages you use Firebug on:
That seems pretty cool to me. (Note that the top link here is a page I opened Firebug, then closed it, seems like Firefox is confused).
Still investigating this idea, comments welcome.