If you go with the refurb Macbook, I'd suggest also looking at these two upgrades:
2 x 2GB RAM sticks:
http://www.memoryexpress.com/Product...16414(ME).aspx
(80 bucks to upgrade to 4GB of RAM)
320GB 7200RPM Hard Drive:
http://www.memoryexpress.com/Product...21563(ME).aspx
(not totally needed, and you can go to a smaller size as well... but you'd be surprised how much a faster spinning hard drive can make a difference)
Keep in mind that the Macbook I linked will perform quite nicely as it is already. It's got everything you'll need in it, and you can also do the dual-boot thing if you still want to run Windows (nothing wrong with that, and it works flawlessly). These upgrades are only suggestions, but they are something that I would do. It's never a bad thing to have too much power!
Again, though... to be clear, these are not "must have" add ons. You should be more than fine with it as it is, out of the box.