Originally posted by monochrome IMHO it he capacity to PM and have one's questions directly answered plays a large part in eventual satisfaction.
That presupposes my l expectation learns through experience that sellers are universally trustworthy and buyers always pay quickly - or - with PM conversation, when they say they will.
My experience with eBay is that despite the ability to talk to one another the level of poor information or different standards about what is Clean, Unblemished, etc. is very high. The lenses I have bought there have been a crap shoot. Far too many misrepresentations with far too much hassle to make it fun. I still get things there on occasion - the breadth of the reach is huge and helpful. New items are less of a problem.
My latest experience (negative) with eBay was a seller that included religious tract material in a package. I'm frankly annoyed that I paid to have spam shipped to me... but the product was nice so they got a positive report from me.