Microsoft recently conducted some interesting studies on running WebSphere on Windows. Their research is published at the website http://www.websphereloveswindows.com/, which has an intro splash that looks more like a flash-based Valentine’s card than anything else. I recommend clicking the "Skip Animation" link and digging into the research information. This is a compelling study to consider running Windows for WebSphere applications rather than IBM OSes and Unix variants.
I look at this information as being another step forward, similar to announcements like integrating PHP with Windows Azure data resources (see http://phpazure.codeplex.com/).
The Stock Trader sample download that was used in the benchmarks for the study includes some very interesting code from a WCF perspective. I recommend everyone explore this sample for more information about the study.