Despite all the cries for Garmin Edge 500 (which is perfectly good), I think the Garmin Forerunner 305 + Cadence sensor is a much higher bang for buck option. It'll cost nearly $80-100 less, and does pretty much everything the Edge does, PLUS it can be used for running. The only drawback is that it has a smaller screen (which can be a good thing, actually.)

You get GPS, cadence, HRM, all watch features.

The main reason to NOT get a Forerunner 305 over the Edge is if you have a PowerTap. The Forerunner will not pick up powertap data. But if you've got enough coin to sport for a PT, you probably don't need to worry about the $80 difference.