I am very very happy with the Forerunner 310XT! At $250, I have a cycling computer with ANT+ compatibility, plus an awesome running computer! The thing can even be used for open water swimming if you put the unit in your swim cap. This is simply the best GPS device for the money. I would choose this over the Garmin Edge 500 even for just a bike computer. I installed the adapter for the wrist band so that I can snap the unit from by bike stem to my wrist band and back in a second. This device and the Garmin connect software have both become vital training tools for me.
The unit is light and the battery lasts 8+ hours during activities. The vibration alert is a nice feature, even on the bike. The heart rate monitor works every time, and the customizable screen displays four data fields. I think Garmin nailed it right on the head with the Forerunner 310XT.