No. I think if a site were to approach 10% of eBay's size I'd consider it. So far I don't think anyone has even approached 1% of their size and that includes: Amazon, Yahoo, Microsoft, and Overstock who all tried and failed.
It would cost me time and money to make our site work with those. There are no buyers there, and no sellers. I'd be throwing away money. I'll make more money and get more customers using that same amount of time improving our service for eBay where all the buyers and sellers are. As would most sellers. If you quit eBay and move there another seller will just pick up your place in a heart beat.
We supported Yahoo and Amazon 8 years ago but nobody used it. It cost me time and money and may have even led to competitors inching ahead back then. Had I kept my focus on eBay back then I would have done much much better. I don't need to learn that lesson twice. If the sellers here leave to do their own thing 2 more new sellers will step in to replace them. And hopefully they'll use Auctiva. I can't say the same for all these rinky dink sites that pop up every time some eBay sellers get upset. And remember not all sellers are upset over these changes. We only hear from the ones that are.
I say these things partly because I think they are true, and partly to provoke. If a bunch people go prove me wrong and some other site pops up that's great and when it gets big enough we'll be there. Right now though I've seen like 10 different sites mentioned. Pick one and everyone go there. Sellers can't even pick 1 place to move to. So even the ones that quit are going to be 100th as effective as if 10 out of 10 went and sold on the same site. The power of the 10 together is much greater than the same 10 spread to 10 different sites.