Mozilla recently released Gran Paradiso 1.9 Alpha 5 (aka Firefox 3).  This is the up and coming version of Firefox and although still in Alpha, I have been running it for several days now and it  is quite stable.

According to the release notes:

Gran Paradiso 1.9 Alpha 5 introduces several new features:

• Bookmarks portion of Places has been enabled
• New crash reporting system, Breakpad. It’s enabled by default on Mac OS X, on about 50% of Windows installations, and not yet available on Linux.
• You can also view crash reports at this site.
• New Javascript-based Password Manager. More details available here.
• Support for Growl notification under Mac OS X
• Support for native controls on Mac OS X
• Miscellaneous Gecko 1.9 bug fixes

Most of these fixes are under-the-hood, so the new Firefox is remarkably similar to the old one!

The major obvious differences are it appears slightly faster (though this could be due to the lack of plugins!) and the pages render better. The major downside is that Gran Paradiso is a memory hog, using 1.15gb of virtual memory on my MacBook Pro! But that is with four windows and fifty tabs open.

Upgrading, as always, disables most of the plugins. I have mixed feelings about that. Some plugins I love and hate having to go without (Adblock, for example) but the majority of the plugins I had in Firefox 2 were downloaded to try out and never used again!

Overall, if you are happy running Alpha software, try Gran Paradiso. You will like the improvements and there are very few downsides.