With SQL Server Data Services, it looks like Microsoft is finally entering the foray that Amazon's S3 service provided. As a Microsoft developer the best part is the integration with the tools and technologies that we use, especially LINQ. If you don't know what S3 is, it's basically a storage in the cloud thats hosted by Amazon.
One of the projects that I worked in my earlier job needed scalability and Amazon's S3 and EC2 services were something that I studied extensively. I'm looking forward to Microsoft releasing an EC2 type of service where .NET code can be hosted in the cloud. This will make it extremely cost effective to build applicatios where you need access to a lot of processing power and storage space but for a limited period at a time.