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-apps.aspx

Enjoy!