ASP.Net MVC for Visual Studio 2010 is available for download here: http://aspnet.codeplex.com/Release/ProjectReleases.aspx?ReleaseId=28527.
There is no new functionality but you should be able to upgrade your applications to target the 4.0 framework (or leave them as is) if you would like to play with ASP.Net MVC on Dev10. Please read the release notes for a couple of gotchas. If you never read release notes, please note the following:
If you are working with Visual Studio Team System 2010 and the Historical Debugger is enabled, Visual Studio might occasionally crash. If you experience this problem, disable the Historical Debugger.
You can disable the Historical Debugger in Tools->Options. Note that this will be fixed in Beta 2.
Hope this helps you develop ASP.Net MVC apps on Dev10
Joe Cartano | Visual Web Developer