It seems to me that every time we release a new service or feature, our customers come up with ideas and requests for at least two more! As they begin to "think cloud" and to get their minds around all that they can do with AWS, their imaginations start to run wild and they aren't shy about sharing their requests with us. We do our best to listen and to adjust our plans accordingly.
This has definitely been the case with EC2's Reserved Instances. The Reserved Instances allow you to make a one-time payment to reserve an instance of a particular type for a period of one or three years. Once reserved, hourly usage for that instance is billed at a price that is significantly reduced from the On-Demand price for the same instance type. As soon as we released Reserved Instances with Linux and OpenSolaris, our users started asking for us to provide Reserved Instances with Microsoft Windows. Later, when we released Amazon RDS, they asked for RDS Reserved Instances (we've already committed to providing this feature)!
I'm happy to inform you that we are now supporting Reserved Instances with Windows. Purchases can be made using the AWS Management Console, ElasticFox, the EC2 Command Line (API) tools, or the EC2 APIs.
As always, we will automatically optimize your pricing when we compute your AWS bill. We'll charge you the lower Reserved Instance rate where applicable, to make sure that you always pay the lowest amount.
You can also estimate your monthly and one-time costs using the AWS Simple Monthly Calculator.
PS - If you have any wild and crazy AWS ideas of your own, feel free to post them in the appropriate AWS forum.