But there are a couple of other possibilities. Some open-source wrapper APIs under construction claim to support a whole set of clouds. In fact, here’s one on Sourceforge; I haven’t personally tried it and can’t vouch for it in any way, except to say that it’s just one example of a handful out there (do a Google search).
I suspect we’re going to see more of these open-source APIs that target multiple vendors. With one of those, you can potentially use any number of clouds. As for the APIs themselves—if you’re not worried about vendor lock-in, then both Amazon’s and Microsoft’s platforms are actually pretty easy to use and are in many ways quite similar. I personally rank them both about equal in programmability.