Although we won't be seeing a final version of Firefox until early next year, Mozilla have released beta 7 to the public while they press on with beta 8 nightly builds. This update brings in the most extensive changes between builds, and although it's not a finished product it is becoming much more usable and stable with each beta.
As DexMorgan points out on our forums, no less than 2439 bugs were squashed between beta 5 and beta 7; why no beta 6 you may wonder to yourself? Well Beta 7 was initiallly supposed to be beta 6, but 2 bugs surfaced shortly after the release of beta 5 prompting a small beta update in order to fix a stability issue on Windows and some rendering and keyboard/mouse focus issues on OSX related to plugins.
To put it into perspective, below are the number of bug fixes between the most recent builds:
beta2 - 684
beta3 - 510
beta4 - 651
beta5 - 650
beta7 - 2742 bugs fixed
You can grab the build here, it weighs in at 7.7 MB