I've been considering replacing my slowly dying Garmin Edge 305 with either the 500 or 800. I'm coming across some "Manufacturer Refurbished" models on eBay with decent looking prices around $170/$230 (500/800). Has anyone bought a refurbished Edge and have positive or negative feedback about their reliability?

I don't know about eBay refurbs, but I've gotten refurbished units directly from Garmin by sending in my old unit with a dead battery or other problem. These looked and worked as new, but came with no manual, cable, charger or anything else, just the bare unit. The Garmin warranty on the refurb was 90 days.

I've bought factory refurbs from NewEgg.com and DrivenGPS.com. One of them (I forget which vendor it was from) after a few months would no longer establish a data connection with my laptop (even though it would still charge through the same USB port). Since it was still under warranty, Garmin had me return it to a local authorized dealer for an exchange (it happened to be REI, of which I'm a member)—no hassles. The replacement has been working fine.

There are some reports that all Garmins (maybe all bike-mounted electronics?) at some point get wonky from the road shock and vibration they're subject to eventually causing circuit failures in the hardware. You get odd symptoms like the unit shutting off in the middle of a ride, or failing to keep track of your current position, etc.

In my experience and from info garnered on the Garmin users' forums, Garmins will get wonky, but most often it's due to software glitches that response to various levels of resets or reinstallation of the firmware. They can suffer mechanical or electrical failure, but much less often.