Best thing I've read in a while about VS 2008 (from Scott GU about the release of VS 2008):
"Browsing the .NET Framework Library Source using Visual Studio
As I blogged a few weeks ago, we will be releasing a reference version of the .NET Framework library source code as part of this release. Visual Studio 2008 has built-in debugger support to automatically step-into and debug this code on demand (VS 2008 can pull down the source for the appropriate .NET Framework library file automatically for you).
We are deploying the source servers to enable this right now, and will be publishing the steps to turn this feature on in the next few weeks. "