I've been using the nightly's for the last 3 weeks and they've worked great without any crashes. I'd recommend upgrading if you're comfortable with beta software as I believe most of the big bugs have worked out. The only major bug I've noticed is that using right click and selecting 'back' doesn't always work.
The latest build moves the tabs to the top which is an interesting change and takes some time to get used to.
It's interesting how FF and IE now differ in layout from top down:
FF: Title Bar, Menu Bar, Tabs, URL, Bookmark Toolbar (default hidden)
IE: Title Bar, URL Bar, Menu (default hidden), Tabs
The latest build moves the tabs to the top which is an interesting change and takes some time to get used to.
It's interesting how FF and IE now differ in layout from top down:
FF: Title Bar, Menu Bar, Tabs, URL, Bookmark Toolbar (default hidden) IE: Title Bar, URL Bar, Menu (default hidden), Tabs