I had problems with 0.8 freezing, crashing, or rebooting my laptop. So far, 0.9 is much better. I think there have been some memory issues resolved, and it is definitely more quick/responsive, in both opening, and in loading new pages. I don't use the extensions, so that doesn't matter to me. I can't use the MicroFirebird theme, which made Firefox by far the smallest footprint web browser I've found. Hopefully someone will put in the effort for that theme. If not, Firefox is still the best browser around.
And thanks GOGF, I didn't even know 0.9 was out until I saw it in your signature. Thanks for having a very useful signature!