Always buy refurbished directly from Apple. You get a full year of AppleCare warranty attached to the purchase and can buy more years of AppleCare after that.

http://store.apple.com/us/browse/home/specialdeals

When a new model launches, that's the best time to buy refurbs on the older stuff. The older Macbook Airs are going for 35-40% off list right now.

I've had nothing but good experiences with this - bought several refurb Macs from Apple and each one has been indistinguishable from a new machine. I always extend my warranty as well.

The only downside is that Apple will charge sales tax, which can be substantial on a $1,000 or $2,000 item. Last time I bought a MBP it was actually cheaper to get a new one from Amazon because they were discounting it. (That was before Amazon started charging sales tax in my state, obviously - otherwise it would have been a wash)

http://www.refurb.me/ is monitoring service for the official Apple refurb store. Because it's hard to know when the product that you want to buy will become available. RefurbMe will alert you by email or SMS to go buy it on the Apple Store.

Ditto that! All my Apple products are refurbished. Working great and 20 to 50% off.

Only if you like to upgrade frequently. Otherwise your prev gen refurbished will run into non-support for the next OS or hardware innovation.

Perhaps for iOS devices, but the desktop stuff can run for a long time on older hardware.

I'm personally using a refurbed Early 2008 iMac that runs Mavericks just fine. It needed more RAM and hard drive space, but that was nothing that I couldn't have purchased when I bought the machine.