I always carry a couple extra presta valve stems with me while on tour. Occasionally those things can get bent if not careful while pumping up your tires, especially when in a hurry and using a small frame pump. Again, just one of those little things that take up no space and yet without, can make for a miserable day.

Yup, that has been a problem for me. And after I filed down one adapter I decided to just file the rest down too. I have a digital Toppeak gauge that is supposed to work with both Shrader and Presta, but using it in Presta mode it loses a lot of air from the tire, so I decided to only use it in Shrader mode.

Good point on the Presta not having a spring like a Shrader, the air pressure should be enough to open the valve when pumping it up.