I definitely agree about the factory refurbs, if you aren't tech savvy, but I think even those are often overpriced.
One thing to be aware of: I sell used computer equipment, and what I generally do is look at it and make notes about what works and what doesn't. This is what some companies call "Refurbishing".
Essentially, they dust it off and wipe the HD, reinstalling whatever the software companies pay them to put on your computer.
That is often a private company "Refurb computer"; note I am NOT saying it is EVERY private dealer refurb, just a common practice. Factory refurb is generally no different; they are just working with newer, better materials.
If you are thinking refurb from a private company, you might as well hit craigslist; then you get the other guy's video games, too. :D
Just my two cents!