My Garmin 305 GPS isn't perfect for sure, but it's remarkably good for cycling. (I have the Forerunner, not the Edge.) It's actually extremely accurate on the bike since distances traveled are greater than on foot. I actually can't criticize my Forerunner's GPS at all on the bike - my only minor complaints have to do with its form factor and screen layouts.

The Garmin 305 Forerunner + Cadence/Speed sensor (optional - GPS will work 100% without it) is the same price as the Rox, as well. Not bad for wireless HRM, GPS, stopwatch capabilities, and when using SportTracks, accurate "corrected" altitude for your entire route based on the GPS map data and online altitude maps.