Extremely slow response with a VS2010 solution

I copied a solution from my dev environment into a production environment and noted an extreme decrease in responsiveness ... e.g., a five second delay between a keypress and its appearing on the screen; 30 seconds plus to go from designer view to code view, etc.

The solution was pretty simple (although it destroys all my breakpoints) -- delete the SUO file for the project so that VS2010 has to build a new one.  Once that was done, performance was normal.