Hi,
I find a presta hand gauge convenient when I use my Mtn bike. When I leave my home I have pumped my tires to max since I'll be riding on asphalt for a while. Once I get to the dirt section I'll use the hand gauge to get the right pressure for the ride conditions. I am too lazy to pump the tire back up again with a hand pump on the return. I have found determining the pressure by feel can often be deceptive.
YannisG