Here is an interesting article comparing Windows Vista and Ubuntu desktop systems.
Are we to the point where we can compare the two? Are we to the point where ligitimate amount of CIOs are going to ask themselves which is better for their business environment? I don't think so (at least in my industry), but others do. Linux is still more of a server and engineering workstation desktop IMHO.
In the next 5-10 years, Ubuntu may be a viable option for people in my industry, but not as it is now. The users and applications aren't ready for it.