I'd take KEH over eBay any day. I have several Nikon cameras and lenses bought from KEH which I consider to have been very good buys. When I did get a lens for my Bronica SQ-A with a defective shutter (didn't check it, ended up with half a roll of blanks!), they gave me no hassle and even held another one for me until the return reached them. This was right on the 7-day return limit, but as it was defective (everything BGN or better is guaranteed functional for 6(?) months now) it probably didn't matter.
Nice people. You won't get the best price selling to them, but their gear is fairly priced and as others have said, conservatively rated.
I have a very nice FM2n I got for $42 out of their as-is bin. Small amount of corrosion where the rubber eye piece used to be, but otherwise works great.