I am leery of factory refurbished machines, this can mean that it was only out on display, used a few hours to demonstrate, to it was abused and sent back and they may or may not have found all of the problems. I found many refurbished machines when I was looking for mine, and for not much more I found brand new ones. Saving a $100 or so now may not be such a wonderful deal a year from now.
Good luck on your search, but, if at all possible go and try one out at a dealer first, even if you end up buying the same model online. My Singer has problems going through some of the seams, and I am only sewing 100% cotton fabric in my piecing.
Good luck in your search! :D