Compuware-backed CloudSleuth published results from a year’s testing this week, and Windows Azure — running in Microsoft’s Illinois data center — consistently proved fastest in running the test application. A number of other US-based providers, including Google App Engine, GoGrid, OpSource, Rackspace, Amazon and Terremark, performed similarly to Azure. It’s also worth noting that the same PaaS solution running in a different data center (for example, Azure operating out of Microsoft’s Singapore facility) performed far less well. Rather than quibbling over whether a particular cloud comes second or third in the rankings, it may be more useful to consider the very clear regional trend; the U.S. is demonstrably faster than Europe, and Europe is significantly faster than the Asia-Pacific region.