Well, I'm a noob, so take this with a grain of salt. I purchased a Garmin 500 and find that after my 1 hr rides, the battery is close to full power. In fact, after I upload the ride to my computer, it's fully charged again. (It charges when hooked up to my computer).
I like the fact that I can upload my ride to both GarminConnect and MapMyRide for tracking and analysis. It's very simple to use and the firmware is intuitive.