hmmm, anyone use this site before?
recertified, does that mean used?
Recertified means that it was returned for some reason (like it was broken under warranty, or defective or whatever) and then if it was broken it got repaired, and then someone with authority (presumably works for Microsoft) inspected it and said "Yeah, this is good enough to sell again."
I think I've bought around three recertified controllers from NCIX, and they all seemed essentially new. I think one had some minor smoothing on the white plastic, but all the parts seemed as tight as new. On another controller, I found a minor scratch.
I've bought plenty of used controllers before (going back to the Atari 2600), and by my experience, it's rare (but not impossible) to find used controllers that are in as good condition as recertified 360 controllers.