I requested this enhancement a long time ago and nothing came along, so I figured it out and have done this through 6-8 versions. With the new admin of 3.1, however, it takes a lot of hacking of core CSS files to get it to work in a good manner because of the two new bars that got stuck in at the top of the screens. :/ The previous enhancement still works but it falls below the light grey bar. That bar scrolls off the top, leaving a gap where it was, so I went to work finding a solution. I'm working on a method of overriding the core CSS, so that they can return to as-shipped but it's not done yet. When (if?) I get it working, I'll send my code to Ozh and see if he'll integrate it.
One thing that you can't do in 3.1 right now if you are running Multisite is select the Hide Header checkbox. It then removes the only current link to getting into the Network Admin screen.
What I REALLY need is the My Sites menu from the new WP Admin Bar to be integrated into Ozh's menu. Then I can do away with that wart altogether because everything else on there is redundant and, I'm told, speed my site up again.