slapfish: nice, I have something similar, only I don't use the bookmark bar, and I've shrunk the tabbar and addressbar down to be really narrow, no vertical space around components.
As for tabs, If I knew of something that was better, I'd be rich, rich, RICH!
Tabs work fine for separating UI, and when you only have a few tabs. When you have 30-50+ open (I had well over a 100 once), and several seperate 'groups' of tabs that have related contexts, then I'm not sure tabs are ideal. I often leave web pages open as a 'todo' list, or because they are relevant background to another tab than I'm working with, for example.
Multiple rows of tabs, colour-coding related tabs, all these things help, but I'm sure there must be something better. I often resort to the pull-down list of open tabs to get a decent overview, and to find tabs quickly, but even that only holds 40 at a time, and needs to be multi-column instead of just a list, at least. The ability to search for open tabs in the 'awesome bar' will be a great help.
I suppose multiple windows, each containing task-related tabs is the answer, but how do you manage, organize, re-arrange, tabs like that in firefox? Drag and drop to some extent but it's not easy. If tabs were at the window manager level, I'm sure it would be more refined, and on top of which there would be all kinds of utilities to do stuff for you.
Still, we have the exact same issue when it comes to managing windows, and the solution is tabs, aided by multiple workspaces. Perhaps there is no better way, but I see things like Apple Expose is quite popular. I suspect a more fluid version of a zooming interface will replace it at some stage, especially with touch interfaces making navigating this kind of space so much easier and intuitive than with a mouse/kb.
There is already some discussion on tabs, for example, here http://jboriss.wordpress.com/2008/06/08/improving-tabs/ The sketches are for a 'tab management' window, which I think is sorely needed (but again, should be at the WM level - too late now though), but something along these lines could actually replace tabs entirely for some people.