September 8, 2011 I received an anniversary email from eBay congratulating me on 14 years of membership (I started a little earlier using my wife's user ID to bid on some stuff though). My feedback is 1124, 100%.
EBay is a valuable tool for finding out what an item is worth at that moment in time.
If I see someone trying to sell a kit I am interested in at a buy/sell/trade forum; I do a quick eBay search to see if that is a reasonable price to pay. I also check Squadron, Great Models and other online sites to see if it is a deal or not.
Likewise if someone is looking for a kit I have, but have no interest in any longer, I check those same sites to see if it is worth it to offer mine for sale. If it is a kit I paid good money for but is not worth that amount right now, I will pass on trying to sell mine and keep it for when the value goes back up.
When contemplating an online trade, I sometimes use eBay and other sites to determine whether or not the deal is a fair trade. That way both modelers get roughly the same amount of value and neither one feels like they were taken advantage of.
I remember back in the day when I could browse all model kits for sale that week and it would take just over an hour. EBay was populated by regular folks just trying to get rid of models or looking for great deals.
Today, many online retailers populate the site as their primary or supplementary store front. It is still possible to find great deals, but nowadays, you have to sift through hundreds of models listed at full retail price to find the guy selling his old, unwanted kits for pennies on the dollars.
Additionally, modelers who once would list kits at a fraction of its worth now raise their asking prices to more closely reflect prices listed by dedicated retailers selling at full price. They don't realize that the buying public would rather pay a couple bucks more to buy new from an actual retailer than to save a few bucks to take a chance on a used kit that may or may not be complete. They get soured because their items don't sell and they are out all the initial listing fees.
I continue to surf eBay daily, albeit not as closely as I used to do. I will randomly search a few pages looking for deals, but mainly use it to find specific items that I want to build.
For those of you who dislike eBay and will never use it, I say stay away. One less person looking for the great deal means my chance at getting an even better deal increase. All it takes is one other bidder looking for the exact same item at the same moment in time to make that great deal go away.
After 14 years, I've learned how to sift through the MSRP prices and find the great deals. I won't share my techniques, but I will say that bidding before the final minute isn't the way to go.