Ok, firstly as much as I like the new interface, it's way too big and bulky. The page dock is cool, but both the dock and the tab bar are now about double or quadruple in size from the original. One thing that makes or breaks a browser is how much screen space it gives you for actually viewing the page. Now if you're running a freaking 30" screen the new interface would be great since you have more screen space than a page would use anyway, but for my little 14" iBook this is fairly horrid. Also, there's a good two inch thick bar below the main toolbar that seems to do absolutely nothing. Yes, you can collapse the dock, but the status bar below is also pretty intrusive, and you really don't get much space with this.
Secondly, full screen looks nice but is highly nonfunctional. The draggable Quicktime-esque control bar is kinda nice but there needs to be a better way to show/hide it, to make it smaller (ie small icons) and to include an address bar so it can actually work.
Overall, even for a beta, just assessing the new layout, it's really too much superfluousness and not enough function.