We have 705 and 305 Garmins on our tandem, but I'll still take a paper map if we're trying a new ride in unfamiliar territory. The Garmins are great if you're following what we call the "blue line" or if you're completely trusting of turn-by-turn directions, but if you're forced to go off program I don't trust the Gramin's to just get me there on a bicycle. I've had enough problems in rental cars. Nothing says "Situational Awareness" like a paper map.
If you do get lost, however, you have the satisfaction of knowing exactly where you are in Lat/Lon.