MVC3 + code-first from the EF4 CTP makes throwing together proof-of-concept apps very fast (and painless!). You don't have to do much besides design your models and you get a functioning site to start with.
Here's a interesting technical interview with Andrew Nurse who created the Razor View Engine for ASP.NET MVC 3. In the interview, he said Razor was his first project once starting at Microsoft.<p><a href="http://channel9.msdn.com/Shows/Going+Deep/Andrew-Nurse-Inside-Razor" rel="nofollow">http://channel9.msdn.com/Shows/Going+Deep/Andrew-Nurse-Insid...</a>
Word of warning that I found and ScottGu confirmed in the comments of his blog post, if you have the Async CTP bits installed and you install MVC3 RC you will lose the ability to use the watch windows during debugging. Just a heads up to make sure you only have one or the other installed for right now.
With this release, the .NET world is getting pretty close to the Ruby on Rails development experience:<p>* dynamic keyword<p>* NuGet <=> gems<p>* MVC scaffold <=> rails g scaffold<p>The only reason why I keep developing my personal projects in RoR is because of Heroku. Azure is still too expensive.