I got a refurbished white 2.0 GHz Macbook just last week. I seriously couldn't tell that this was a used computer at one point; it smelled like a new Macbook, had no cosmetic defects, came with all of the accessories, etc. What's the difference between this and a new one? It was in a brown box. That's all. Oh, the other difference: it came with an 80 GB hard drive right off the bat.
You seriously can't go wrong with a refurbished Mac at all. They also come with a standard one year warranty with a chance to buy a three year AppleCare warranty. They're also $200 cheaper, has a high chance of having free upgrades, etc. I also have heard of a guy that got a fully loaded refurbished black Macbook without paying a single extra penny.