Of course right away all you extensions don't work. But that's my own fault for installing before the authors even know this release it out, let alone release their updates. Don't worry though, in most cases its just a matter of changing the extension's maximum supported browser version. Shouldn't take long. And with every release of FireFox they seem to take the most popular and useful extensions and build them in. So quite a lot of those extensions that I couldn't live without are obsolete.
Like that one that put a little 'x' on each individual tab so you can close it without viewing it: built-in. (of course all the smart people knew that middle click does this already)
And remember that Google Anti-phishing extension from a while ago? Built-in. But its not quite the same, it doesn't check every page you visit with Google's servers. (it has that mode if you'd like to broadcast your usage) It periodically downloads the blacklist of known phishing sites to check locally. No broadcasting, good job.
Google suggest, where they try to guess what you're searching for as you type: Built-in. And its not as annoying as it is on Google's main page where its actually typed for you. They unobtrusively list in a dropdown, which I'm cool with.
Restart with tabs: built-in. This was a sweet extension, on a crash or restart (like after you update all those extensions) it loads up all the tabs you had before it closed. Along with an "undo close tab" this bit will solve a lot of your headaches from faster than though clicking.
In-line spell checker: built-in. I was so happy the day I found that extension, cause I can't spell crap. Hey! I spelled it right!
So, nice new features. But I already had most of the UI ones, it just takes fewer ad-ons to create the same experience. Not a must-get-immediately download, but its gonna be sweet when you do...
Firefox 2 Beta 2 Start Page