Henry Ford is famous for his lack of flexibility over the Model T: You can it in any colour you want, as long as it is black.
I think Amazon have taken a leaf out if his book, when offering their Windows instances: You can have any size disk you want, as long as it is 30Gb.
Don't believe me? Go on, try automating the creation of a 100Gb boot disk Windows machine. Or creating one from the web interface, without any post-configuration steps in Windows itself.
(I'll save you the Google: here is the AWS engineers telling you the multiple steps needed to achieve that. The instructions are different depending on the exact version of Windows.)
In fact, try automating anything to do with Windows configuration, using EC2. You can't. It can't be, won't be, scripted. You always have to log on afterwards (going through the EC2 Console to get your almost-impossible-to-type password) to do something. Usually quite a tedious and time-consuming something.
The bottom-line: Windows is not designed for the cloud.
...and yet, some of my clients, and some of my potential clients, insist on trying to use Windows anyway. The cloud is where they feel they should be, so people want to move their legacy apps there. Whenever I ask them how they do it, or why they do it, they seem to find justification. It is the cloud, look we're scaling. We're faster. It works! Like a man let out of prison, and running free in the meadow... only he still has the manacles and chains from his time doing time. Am I carrying my metaphor too far by wishing people would stop and take the Linux axe to the manacles before rushing off to the meadow?
Are you an expert at automating Windows on EC2? Please post a comment showing off your knowledge. I'm willing to learn, and will edit this article if you convince me it can be done :-)