I have. I bought a replacement magsafe from one of those little outfits that buys "old macbooks in any condition! ca$$h today!" and refurbishes them. I paid almost full price for it thinking it was OEM, but when I got home and matched it up to my extension cable, it was obviously a cheap knockoff. Worked well enough even though it was unsightly and difficult to use (the extension cable was really hard to slide on and off), but at $85 compared to OEM at $90, why bother?