I have just read about another great new feature coming in Visual Studio 2010 on Scott Guthrie's blog. Over time the web.config files associated with .NET web projects have got larger and larger this is because version 3.0 and 3.5 of the .NET framework share the same machine.config file meaning that configuration for the newer features had to be put in the web.config.

.NET 4 changes all of this with a new version of the machine.config file specifically for V4 of the .NET framework. This will mean much cleaner web.config files with just the information relevant to your project meaning you end up with web.config files maybe just a few lines long rather than 200+ lines long.