I hope they keep plugging away at making their developer tools better. I use Firefox as my main browser, but I often have to switch to Chrome because Firebug's performance is pretty crappy even on my Ivy Bridge laptop (with 16GB of RAM).
We are indeed plugging away on the tools (and they are getting better each release :)
Firebug will be getting faster as well as they are working on putting Firebug on top of the new debugging API in Firefox (which has much better performance than the old).
My solution is to create various profiles for my different browsing needs. I have my "webdev" profile which has a lot of web development extensions including firebug, I also have my "main" profile for most browsing, the "wastetime" profile and some other profiles.
While my main profile is open most of the time, I can open webdev using "firefox -profileManager -no-remote" for some javascript debugging and close it when I am done without messing with my other open profiles. If I get bored I might fire up "wastetime" to browse some websites, or the "noextensions" profile to check a website with no extensions (sometimes noscript, better privacy, adblock plus, ghostery or even pentadactyl might mess up some website that I visit).
A really cool bonus is that with each profile I can save the opened tabs, so for example I have a "coursera" profile and it has all the tabs I need for the course I am taking (functional programming with scala). So, when I am studying I only need to open that profile either by itself or in addition to other profiles.
