I have both valves on my bike. I have a cheap wheel on the rear (it actually came off the imfamous Denali), it is drilled for, and has, a schrader-valve tube, it isn't even quick release, so I carry a little wrench in my supply bag. My front wheel is a basic Alex rim with quick release, made for presta-valved tubes. My floor-pump and frame pump both have dual-heads (two different holes to accept either valve), when I move from one valve to the other I don't have to fiddle with the head (unscrew or turn something over, etc.). I do carry a presta-to-shrader adapter, just in case air from a gas-station might become an option of choice, but I've never had a reason to use it.

I came to this set-up months ago because it was my best option at the moment and have stayed with it because there isn't a compelling reason to change it. I do see a slight potential problem if I have a flat on the schrader tube, can't repair it on the road with my repair kit, and am left with a presta tube (I carry a spare presta tube with me) as my only next option, but I could probably get home with a presta tube (the low PSI from the mini-pump would probably be a good thing in this case), and there would be no issue if I got the widget to make the stem-hole adaptation.

As a side note I think using both valves on the same bike gives you greater insight when the schrader-verses-presta debates break out.