Ars Technica reports that an independent vendor has benchmarked numerous cloud providers over the past 12 months and found that Windows Azure is the fastest among them:
The Windows Azure data center in Chicago completed the test in an average time of 6,072 milliseconds (a little over six seconds), compared to 6.45 seconds for second-place Google App Engine. Both improved steadily throughout the year, with Azure dipping to 5.52 seconds in July and Google to 5.97 seconds.
The uptime of the Azure cloud is also very respectable with the Chicago location managing a 99.93 percent uptime over the past month.
Hyper-V according to me 