New types and methods for .NET 2.0 and 3.0 SP1 (red bits)
With the release on .NET 3.5 there will be changes in the "red bits", so called .NET 2.0 and 3.0 libraries and they are supposed to be minor changes (as opposed to "green bits" = new libraries).
New additions to GC suggest that the developer will gain more control over how the GC functions. And you can fine tune it to you needs.
The complete list of the "red bits" is available here.