Make sure you got a Refurb that is Apple Certified. Last xmas, the day after, my g5 Mac Pro died. I had had is for 3 years, no problem. I bought a used one online and 6 months to the day that their warranty expired, it died. This one was sold as used. I took it to the Apple store in Palo Alto, CA, and they examined is and told me I would have to replace the motherboard and other items. If I hadn't lucked out and the previous owner had bought the extended Apple Care plan, the repairs and parts would have been over $1000.00....which adds to the frustration. Because I bought the used one to replace a dead one that shouldn't have died.
What I learned is, if I buy again, it will be refurbished. But check that is has Apple Care and that you can extend that care after it expires. If it's included with the price, make sure you know the dates and pay attention to signing up immediately. If the previous owner hadn't had the apple care still active, after buying the used computer for $700-$900 dollars and then the prospect of buying another six months later or paying for repair. With the warranty care I just had to pay for the gas to get to the store twice...which since the Apple store is 200 miles from me, that did cost quite a bit. Come to think of it, after all of this, if the Apple Care plan hadn't helped, I may as well have bought a new computer outright. Can afford that in this economy and running a small business. Now I live in fear that this xmas this one will die. Funny, I never had these deaths when I had the old beige boxes.
So, make sure that you can extend the warranty out to the 3 year mark, it's cheaper that a motherboard/logic board or replacing guts yourself.
Also, I will not buy a used computer from the company I bought it from again. After buying the same computer to replace the dead one, this confirmed my thoughts that it was a design flaw with that model