I have the 12 inch 1.33 and I have been extremely delighted with it. That said, my friend just bought a 15 inch 1.5 and I'm very impressed with all the features, especially the lighted keyboard and the slight speed gains with the 5400 RPM drive. I'd say the $400 price difference is well worth the "extras" you get if you have the money.

I wouldn't have any problems with the refurbished model, especially since it carries the same warranty as a new one, though maybe the case might have a few marks. One option that is a must-have is AppleCare to extend that warranty to 3 years.