Large RPC Libraries
Revit 2011 could potentially hang at startup when the ArchVision Content Manager was set to utilize a large RPC library. After applying update 2, accessing larger libraries should be more stable with Revit 2011.
Shadow Display and Linked Revit Files
When a host Revit project contains a linked file[s], typically with varying elevations or insertion points which were modified after insertion, shadows would not always cast as expected. This behavior was resolved with update 2.
Additional information for the symptom of this issue was documented in a few discussion group posts here.
Material Dialog Stability
Some users previously reported a crash when accessing the materials or rendering dialog. While the previous technical solution typically improved this behavior, after applying update 2 this should be improved as well.
I hope this helps!