I've purchased a MacBook Black refurb about 3 years back from Apple online store itself - and it arrived as though it was spanking new. However, a couple of nitpicks to relate to that experience.
- The refurbed MacBook Black came not in the original box, but a box with the word "Refurbished" labeled prominently.
- The resale value of a refurbed Mac drops when you eBay it or put it on the second-hand site for sale, especially if the buyer knows its a refurbished. It's more about perceptions than anything else.
- There was a small, teeny, eeny, weenie hairline scratch on the top of that MacBook Black.
All-in-all, YMMV. However, I'd say for the savings you enjoy, it is definitely worth it getting a refurb unit. Just make sure you get it from Apple Store, and not some other 3rd party reseller or channels.