Couple of often overlooked features I really like in Windows Vista Build 5456, take a look at the improved glass look compared to the public Beta 2 release too.
The Task Manager now has a services tab so you can see what services are running, but also features descriptions on running processes, very handy. One thing I still think needs improving is auto-resizing the columns with the window itself.
I love the new Resource Manager, really kicks ass. Nice to have access to what addresses the machine is connecting to without using the command prompt or a 3rd party tool.