Yes, you read that right: Microsoft's cloud service Azure topped the list of 25 different providers in a report out this week by CloudSleuth, just slightly edging out Google's App Engine. CloudSleuth uses the Gomex performance network to gauge the reliability and consistency of the most popular public IaaS and PaaS providers. They run an identical sample ecommerce application on a variety of popular cloud service providers and measure the results over at least six months of historical data.
(A summary graph from the report is above.)
The report, which is available here, shows a marked difference between Azure servers running in the US (near Chicago) and those running in Singapore (which lagged the list).