The second beta build of "Bon Echo" (what will become Firefox 2.0) is nearing completion, so I am officially switching to the nightly builds for my browsing needs. And I've already been quite pleased. By default, the nightly builds come configured to use the nightly update channel. Through this channel, you can receive each day's updates just by using the Help » Check for Updates... menu item in Firefox. They get downloaded, applied, and the browser is restarted. And with the new session saver feature in Firefox, you start right back where you left off when you downloaded the updates. How cool is that?
I still dislike the theme, and the list of bugs written against it continues to grow. Thankfully, the list of fixes is also seeing some growth. Hopefully things can get polished up by release time.