For my new workstation, I installed the 64 bit version of Windows 7 Enterprise edition.
Install from start to first log in took 15 minutes.
System reboot from pressing shutdown to seeing the clock on the desktop 34 seconds!
The install is currently occupying 12.6G of hard drive space on my Intel X25-M SSD. That includes all of the latest Windows updates and: Adobe reader and Flash, Amaya, Firefox, OpenOffice.org 3.1.1, Sun JRE and Windows Live Essentials.
I am reasonably impressed by the performance of Windows 7 Enterprise edition on the new workstation. If you must use a Windows operating system, Windows 7 is a pretty decent choice. Be sure to purchase the 64bit version of Windows 7 Professional.