I downloaded it a couple of days ago just to have a feel of upcoming Firefox. I was expecting some kool features and no doubt I found them. It is much lighter and faster than previous version.
The tools menu is changed a lot and has been made more organized. New icons and all! There is spell-check in new Firefox – I am loving it. The UI is made more friendly although in this version, I can’t drag tabs without opening them. Whenever you click a tab and start dragging, it gets open and you loose track of currently opened tab. I used to enjoy this feature of previous version. Another thing is that it crashes a lot. Lot of extensions are outdated the time you start Firefox 2 for 1st time. And you loose those ultra features/comfort! I managed without them provided it was the one I liked more than the previous one and as it was mentioned on download page that it is for testers only. anyway, there is round about to get your old extensions work for new Firefox provided you rely on them. Here is the Nightly Tester Tools which fakes your browser to feel that old extensions are already updated for latest version. I myself is still testing it. So can’t say much about it. After you install it, restart Firefox. Go to Tools->Add-ons. Disabled extensions are grayed out. For the ones which you want to use, right click and click Make Compatible if you want to be on safer side in order to test extensions one by one and detect which can cause problem. If you want to use all extensions in one go, you can click Make All Compatible. You will need to restart Firefox and all is done.
If you want to test it, here is the download link for window users – Firefox 2 Beta 2. Here for mac users – Firefox 2 beta 2.