Survived the Slashdotting because his site is hosted on MobileMe ;)

I noticed that you didn't mention Mosso, one of the first large scale cloud providers that has been doing this for years. They are a division of Rackspace as well. As far as robustness is concerned, there was a great write-up of the Mosso platform last week on this blog: http://matthewsacks.com/techblog/2008/09/23/rackspaces-mosso-hosting-cloud-review/