After maybe two minutes of use, I have to say that one thing about this browser is especially useful for me, and I think for most of the Internet users. I am talking of course about build in Spell Checking which is just great. Now I'm writing this fast post, and Firefox is looking after my spelling. It is much more convenient than using ABS button. Additionally I checked if there are any others languages in spell checking than English, and of course there are plenty of them, including my home one - Polish.
The next two features that are very seen instantly is refreshed look, and improved Tabbed Browsing. Now, each tab has its own close button, which is, I think, better than before.
Next, very useful new thing about Firefox is so-called Search Suggestions. Starting typing in search bar, gives a list of suggestion from search engines. For example from Google or Answers.
Of course there are many more new features than those for example: Session Restore, Live Titles, Live Bookmarks, Streamlined Interface, Phishing Protection, Protection from Spyware ..... List of all is here.