I've been testing the RC2 release candidate for a couple of days, so far it hasn't hiccuped, pages do load faster with this release.
You have four options for Bookmarks, Unsorted Bookmarks Menu, Bookmarks Menu and Bookmarks Toolbar and adds a most visted link as well. I think it may be an overkill, instead of keeping it simple.
I'm still not a RSS feed fan yet, but you have an option to always use live bookmarks.
If you have more than one tab open, you will be prompted. Do you want Firefox to save your tabs for the next time it starts? So it gives you same option as it automatically does if it would crash.
It does look for suspected attack/Malware sites and suspected forgery sites, how well it works, I don't know I haven't found any yet.
You have an on the fly rendering engine to view an IE7 display, in the status bar, it has additional options, to open in new tab. This is good for web developers to be able to view there web designs on the fly.
I'm sure there is more, but a good start.
Well it's getting close to a final release.
Here's what you see when first install the RC2.http://en-us.www.mozilla.com/en-US/firefox/3.0/whatsnew/