There's still a lot of debate about this, but it's working great for me (right now as a matter of fact).
I didn't finish this article yet, but it made one point that caught my eye. Organizations that are still using Windows XP (or even Windows 2000) are perfect candidates for switching to Linux (Ubuntu was recommended) as they will be facing the need to upgrade their operating systems and hardware just to maintain updates. By switching to Ubuntu; they could avoid the cost of both the software and hardware upgrades.
I'm running Ubuntu 8.10 on a very old "throwaway" laptop (a Dell Latitude C640). It performs better than the Dell D610 that I use at work running Windows XP.
Time will tell if Ubuntu exhibits the kind of decay in performance that XP does after installing and uninstalling applications.