This is now live from CLR's team blog. This paints a more complete picture than what I talked about in my "What's new in 4.5 GC" Channel 9 interview which mostly focused on Server Background GC.
http://blogs.msdn.com/b/dotnet/archive/2012/07/20/the-net-framework-4-5-includes-new-garbage-collector-enhancements-for-client-and-server-...
What makes managed code, “managed”? Most people would point to the garbage collector. Automatic memory management makes a tremendous difference in programmer productivity. And when garbage collection improves, all .NET applications benefit. Abhishek Mondal, the program manager for GC on the Common Language Runtime, and Maoni Stephens, ...
As programming with .NET has become prevalent on all Microsoft platforms, targeting multiple platforms at once becomes a critical desire amongst developers. In fact, we see the future of library development moving to supporting an intersection of platforms rather than targeting just one version of the .NET Framework at a time. Mircea Trofin, ...