Personally I think Ebay is phenomenal. I can peruse items 24/7 and not have to attend any train shows. One thing I dislike is driving to a train show, finding a place to park, pay the admission fee, look through table after table and not find what I am looking for, yet leave empty handed. The last one I went to was a few years back when I was in my early 50's and boy did I feel young!!
Just about all of my purchases were great buys, only a few did I have to send back after it stated no returns due to a mechanical problem not specified in the auction. One thing that I do look for is that they say "tested", or "works as it should". If you find an item that says "needs a cleaning", "needs TLC" or "not tested", it's best to move on. Sooner or later I will find pretty much what I've been looking for, then of course I'm not really picky. If it has a few scratches or other imperfections I'll still buy it as long as I don't have to return to Ebay and end up buying another part just to return it to operational condition.