Buying a Refurbished Mac
For background, see How to Choose a Mac.
Apple certified refurbished models have the same warranty, same eligibility for AppleCare, etc.
A refurbished unit is tested and certified to work as new (and possibly might be less likely to fail than a new unit since early “burn in” is done, and it has to have a complete assessment prior to resale).
Some buyers return Macs for no good reason at all, and those units go into the refurbished pool; Apple can’t sell them as new. Refurbished units are not beaten-up stuff, though they might have a minor scratch on a case (for example). But in my experience they look just like new.
Remember that new or refurbished, there is always some failure rate; a new unit is no guarantee.
As a bonus, a refurbished unit can generally be returned, even if it was originally a custom configuration (Apple’s policy could change, check before buying).
Refurbished systems do not allow custom configuration, but often there are several configurations available which approximate the custom configuration you might have chosen anyway.
I now always buy Macs as refurbished when I can find a model meeting my requirements. The only reason not to buy refurbished is when the model you need/want is not available, or doesn’t have a key component you need and can’t easily obtain otherwise (eg a faster video card).
I bought my Mac Pro quad-core 3.0GHz refurbished with the higher performance graphics card at 15% off. I also bought my 8-core 2.8GHz Mac Pro as refurbished. I did not buy my Mac Pro Nehalem refurbished, because a timely review for this site demanded buying one immmediately. Were it not for that, I’d have waited for refurbished units to become available.
Refurbished offerings include MacPro, MacBook Pro, Macbook, iMac, displays, accessories, iPod and more.
Check the refurbished page at the Apple Store, and if you don’t find what you’re looking for, check every few days, because new “stuff” shows up on a regular basis, especially when new products are announced.