Microsoft designed WCF seriously with all major basics taken into account: performance, security, and robustness/stress. I am proud as being part of the team. You might have seen the data that Saurabh, our performance Program Manager, posted in his whitepaper. We have competed ourselves for many of our existing technologies.
So it was not a big surprise to me when Greg Leake first showed us the data that he got with his implementation of the Stock Trader performance benchmark using WCF three months ago. Yes, we are faster than WebSphere, significantly!
Greg’s .NET StockTrader sample was recently published here. You can also find his detailed analysis document from here.