I've had a pretty good experience - but it was from a bike shop. I called and talked to them before I bid.

The bike did come with about $100 worth of stuff my LBS needed/wanted to fix - bad adjustments (could be shipping damage), wrong cable components (brake straddles), etc. They wanted to make it perfect because they love the bike, so I let them (and they are almost always right, and take *really* good care of me usually). But, the light that came with the bike was just recalled by Peter White because it can blow at high speeds. The seller is now (2 + months later) working with Peter to make sure I can get a replacement light even though I wasn't an "original purchaser."

I've had terrible experiences with other things (like a laptop in "excellent" condition with a cracked case). That guy wouldn't give us money back unless we agreed to leave positive feedback. Jerk.