For cycling in Europe, I use a Garmin GPSMap 60Cs and a handlebar bracket along with the Europe Navigator software. My trip enjoyment is far above when I did not have this setup. The GPS lets me remap or reroute anywhere and never get lost. It also shows every little goat path of a "road" you think might be someone's driveway. The only time the routing fails (even in bike mode) is with "bike only" no-auto paths and then it routes you to hell and back over whatever autobaun is near, until you are back on a routable road and then it takes over normally again.
Super cool being able to bomb unknown switchback decents and know what's coming up ahead, ride through dense cities without knowing the signage and traffic flow (one-ways, etc), and tell a tour organizer his route stinks and you're heading over that other pass over there to the right...
I have a few beefs with Garmin though:
1. The biggest problem is that software is licensed per GPS device and not per individual. That is moronic. Obviously I only use 1 device at a time but would like to own multiple devices and not pay $100-$300 each license X each device.
2. The handlebar mount sucks as a slight road bump can jar the GPS from the mount. I improved it by simply adding sticky-back velcro to the sides of the GPS and then wrap the grabber velcro around the underside of the mount.