It's one place to update everything and can be syntax highlighted and formatted quite neatly.
You end up with something like this. This is only an excerpt, the whole thing is quite huge. You can then string your macros any way you like. The fanciest bit of this is the conditionals at the top that I use because some sln's that include these projects are sometimes in different places, and there was no other way I could think of to correctly set the path.
$(ProjectDir)..\..\..\ $(ProjectDir)..\..\..\ $(SolutionDir) WF_DEBUG; _DEBUG WF_RELEASE; NDEBUG WF_FINAL; NDEBUG WF_PC32; WIN32; _CRT_SECURE_NO_WARNINGS; $(FORCED_ENVARS) $(WF_DEBUG); $(PC32_PREPROCESSOR); __PLACEMENT_NEW_INLINE