It REALLY depends. I won a new iPod Touch off there, brand new, for $230, that was good. I also bought a new Treo phone which turned out to be a crappy version that had glitches.
It really depends on the seller.
I've purchased and sold quite a few things off of eBay, and I've found that it is best to NOT purchase anything from Wholesalers or Powersellers that have sold more than 10,000 items. While you may think they have more experience, they don't give you as good of quality in shipping it off quickly, and usually don't give you a quality product.
NEVER BUY REFURBISHED.
It will always turn out to be crap, if you can't see a picture of the actual product your buying, do not buy. The few "light" scratches might be right in the center of the screen of that fancy new iphone.
But I digress, You can certainly find good things on eBay. If they have pictures of the actual product, have good feedback, and the price is right, I would buy it. Make sure they have a good refund just in case though, this is crucial.