Here are some "Things I Have Noticed":
- It's faster, it launched faster, it loaded pages faster and it ran faster even with many tabs open.
- The addon manager will list recommended addons and will allow you to search for addons from the manager interface!
- A little star icon has been added at the end of the address field. When you click the star, the page you are on is bookmarked, if you click it again you get the dialog to name, organize and tag the bookmark.
- Bookmark Tagging. I love this, you can add your own tags to the bookmarks that you save allowing another dimension for organizing and searching.
Keep in mind that some of your addons may not work with the new version.
Oh and try to download it on the 17th if you can. They are trying for a world record for most downloads in one day.