Familiarity? Most of all it seems to have achieved familiarity as developers in .NET area can quickly ramp up to the cloud. Google lacks this in its cloud initiative as its has stuck to python as development language and framework and has recently launched a beta of Java, which make developing web AJAX + cloud based applications a breeze with the standard Eclipse IDE.
Simplicity? Atleast the development environment requirements are not simple setting up development environment can take long time - downloading and installing various components. No single installer there! Microsoft installer technology is not elegant and speedy but its a separate topic.
Cost ? It remains to be seen.
One may sign up for Community Technology Preview (CTP) of Microsoft Azure at www.azure.com. I tried building a simple application in C#/ASP.NET.