Well, I've been an ebay seller for years (on and off PowerSeller status) and up until recently I had been very happy with selling on eBay. Recently however, they slanted their policies so greatly in favor of the buyer, that its been hard for me to stay on there with good conscience. I don't like supporting an organization that doesn't care about its sellers.
I've since switched to mostly selling items on Amazon and been very happy with how quickly they sell (surprisingly so). Amazon charges higher ending fees, but no listing fees so its almost a wash between the two in the end with the added benefit that Amazon items will stay up longer for free, while you have to pay to keep re-listing on eBay.
Some items are still better suited for eBay though, so despite my reservations, I do still list an item on there every so often, but I tried to avoid it if possible.