Got the Yubikey (Black) last Christmas about a week before and at first, I was paranoid about the quality of the key as far as the contacts being so exposed as well as just the durability.
After reading about people keeping this on their keychains, putting it through the washer (Accidentally) several times, running over it, etc and it having survived, I decided that I would just trust what others have said about the quality being superior.
This is little in the grand scheme of things, but for about the past 4 months, I have carried the Yubikey on my keyring and to this date, it still functions good, looks quite new (A little darkening of the contacts however), and has resisted scratching from being around keys, coins in my pocket and even dropped hard on asphalt with other keys.
I am very impressed with the Yubikey's construction quality and recommend it to those that ask about it on my keyring.
I only have one complaint with this key though, it is very hard to press the button when used on an Aluminum keyboard from the iMac's usb slots on the side. But - this is easily solved with an extension cable or hub.