The XPS One 27" arrives with Windows 8 pre-installed and this is the 64-bit edition. Our WEI score is 5.8 (desktop graphics) with the other scores higher.
No updates were installed by Dell at the factory however they do add some software which includes Cyberlink's Media Suite, and Windows Essentials along with an Office trial. Thankfully they also go with Microsofts in-built anti-virus/security software rather than a bloat filled alternative.
Finally also present on the system is a small tutorial application which talks new users through some key aspects of Windows 8.