>>>I didn't use too many - about half of them work, some got replacements, others later.
>>
>>All extensions I'm using got upgrade to work with FF3.
>
>The ones that still don't are the ones I can live without (like Firebug - I'll need something like that next time I develop a web app, not sooner), with the honorable exception of mouse gestures, which I really wish I had again. There seem to be nice replacements available.
>
>Other than that, everything important does work.

Firebug seems to work Ok with FireFox 3.0 My colleague re-installed it for me.