Get motivated to hammer out the miles!
Simply put, the Edge 500 rocks. You can move it from bike to bike, or even throw it in your pocket for a run or hike, without any fuss over speed sensors or wiring. It's excellent motivation to push it on a ride to reach your goals for speed, distance, or elevation gain (yep, it tracks total elevation gain).
I upload my data to the free Garmin Connect service (see http://connect.garmin.com/features) about once a week. From there you can map your ride, analyze performance mile by mile, and even post it to Facebook so your riding buddies can view it.