Buying a Computer: New or Used?

For the business my spouse wants to start (I am not ready to give up what type of business it is just yet), she needs a new computer. The 4 year old, first generation Intel Centrino, Dell laptop, with 512 MB RAM is just not going to cut it. We have had a lot of discussion about the brand of computer we are going to buy. We are fairly confident that we are going to settle on an Apple iMac -- while the cost may be a little bit more than a <Dell, HP, Gateway, insert your favorite vendor here> PC, the fact it can run both Windows and OS X just makes it a no brainer. And with the business my spouse wants to start I can see her switching back and forth between operating systems. And, the new and previous generation iMacs are just sweet looking and designed so efficiently!

Now that the "What type of computer are we going to get" question has been answered, we are faced with another dilemma. Should we buy new or used? The fact is, the previous generation iMacs had Intel Core 2 Duo processors in them, etc., and would serve just fine for my spouse's business. And now that the new iMacs were announced back in August, these previous generation iMacs can be found "discounted" on eBay and other sites.

I have always leaned towards never buying a used computer. I like my computers "clean as a whistle", so to speak. So buying from an individual on eBay scares me a bit. There are reputable stores, like even Apple themselves, that sell refurbished computers. And notice above I put the word discounted in quotes -- I am not 100% convinced that the value you might be able to get from a used/refurbished computer will really outweigh having the latest generation and never touched machine. The new iMacs start at only about $1200; add another 1GB of RAM and you are looking at $1300 or so. Not too bad. Amazon has a $50 rebate too.

So what is your opinion? Would you buy a used/refurbished computer? If so, from where would you buy such a computer?