It's looking pretty slick so far. The new toolbar looks to be build with a minimalist approach, much like Google's Chrome. In fact, I don't see much of a difference between the beta and chrome after a few tweaks, and by tweaks I mean editing userChrome.css and rewriting the code! Personally, the first thing I did was move the tab bar to the very top line. By rewriting the file, you can do things like change the default font size and color, move icons around, and make your own transparent image backgrounds. Being able to change the font size can be really interesting in Linux, due to some font size issues.
Here's my layout
Looks like Chrome, right? Yeah, no kidding. From my slight experience with Chrome, it's almost exactly the same, except the address bar isn't integrated with the Google search bar. The search bar is still located on the right of the address bar just like it was in the older Firefox.
Firefox still has all those famous apps too, even some new ones.
One interesting app which GodofGrunts showed me, is called Tab Candy. It allows tabs to be better organized.
Check this out
Unfortunately, the Tab Candy app is not included with the Firefox 4 beta on the official Mozilla website, nor is it available as an extension or app. Instead, if you want to try out Tab Candy before the official release, you have to download Firefox 4 beta Here.
The official Firefox 4 release, including Tab Candy, is scheduled to release in November. I can't wait.