From the supplied templates, you can create a new Visual Studio project for a cloud service with Web and/or Worker roles, a cloud sequential-workflow service, and Live Framework mesh-enabled Web applications with or without Silverlight support. I would say that getting to "Hello, World!" with an Azure Web role might be the second most complicated "Hello, World!" application I've seen, after Microsoft's own Workflow version, but it really only requires adding one line of code or HTML to the project generated by the Visual Studio template.
This snapshot of the developer portal for Azure hosting, storage, and Live Services shows where I uploaded, tested, and promoted my iwhello1 application from staging to production. At the time, it was live at iwmh1.cloudapp.net and returned "Hello, InfoWorld" to the browser. This snapshot shows a management page for .Net Services and SQL Services.
If you use Azure storage, you need to be aware that the URIs are different for addressing storage services in the cloud and in the local fabric. Consequently, development proceeds in steps. You start by running locally, then you change the storage URIs to move to mixed mode, running the application in the local fabric against cloud storage. Next, you publish your application to the cloud, test it at a staging URL that includes a GUID (globally unique identifier) as part of the address, and finally promote it to a production URL.
There are many ways to run applications in a cloud. Amazon EC2 running a Windows Server 2008 image is probably the closest equivalent to Windows Azure and likely to be the top alternative to Azure for experienced ASP.Net developers who need capacity on demand.
Developers with enough experience to be comfortable in multiple languages and multiple operating systems have more choices: not just Amazon EC2 running other images (such as Ruby on Rails on Linux with MySQL) but also Google App Engine (Python/Django), Force.com, and the like.
Given Azure's preview status, it's difficult to say anything meaningful about its competitive position. We don't yet know what it will cost, and it has no track record for reliability at this point. What we do know now is that it's a well-thought-out cloud computing architecture that should be easy to learn for existing ASP.Net developers.