Here's one person who uses a microscope to check the edges of tools when sharpening them. While I don't think I'd go to that extent on a regular basis, it might be cool to occasionally look at a blade up close to see if there's room for improvement in sharpening technique. The microscope would probably be fun to mess with on other stuff too and, for 50-60 bucks, I might order one just because I'm a gadget geek. 
http://toolmonger.com/2009/07/03/dealmonger-celestron-44302-handheld-digital-microscope/

http://toolmonger.com/2009/07/03/dealmonger-celestron-44302-handheld-digital-microscope/