Maarten van Stam has a nice tip for isolating specific changes made in SP1. Check out his post here, or just run this search and youâ€™ll see the list of 902 pages worth of doco changes.
You can then narrow that further by selecting one of the one of the Refinement options:
Refining by Visual Studio Tools for Office and Visual Studio 2008 for example gives us 306 results:
Speaking of VSTO related stuff specifically, Christin Boyd has a rundown of the VSTO SP1 enhancements here.
Technorati Tags: Visual Studio 2008 SP1,VSTO