I suppose you are using the Azure emulators from azure SDK to test the cloud environment, I have also tested with them, however they don`t give the perspective of the actual cloud.
Regarding sitefinity in Azure the startup is slow, one because the sitefintiy application initializes slowly because of preluding some of its resources (this will be no more from sitefinity 6.0 and the start will be much faster) and second running in the cloud virtual machines is slower than running standard asp.net application.
Regarding the page load times once a page is cached on the application pool of the virtual machine where the site is running it is retrieved almost as fast as on dedicated server.
All the best,
the Telerik team
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