I used to be on the Firefox nightly bandwagon. Then things got unstable and I decided that ... well ... I'd stick with the stable builds. I've wanted a 64-bit version of Firefox and with all the great performance improvements I've been reading about every day, I decided to try the bleeding edge of Firefox again. This article about FX8 for x64 convinced me to give it a try. With Flash x64 (beta) installed, I'm able to play my games. Unfortunately, quite a few addons are not compatible, so I'm using the Compatibility Reporter to submit those. We'll see how long I can live without them.
about:startup shows that my startup times are 1/3 of those from Firefox 5. Memory footprint, with the addons I still have enabled is about 320 MB according to about:memory.