Hi Michael-
I like the informal auctions otherwise for the same reason bazamu mentioned - often I'm not the first to see things, but I would love to have the opportunity to purchase.

The only thing I don't like as a buyer is if there is a clause saying they don't have to sell it if the price isn't high enough, which seems a bit nutty to me and somewhat a waste of buyers time. My preference as a buyer would be to see auctions say "I will sell for any price above $_____, and have the right to end the auction and sell at any time to someone offers me a crazy price." :)
I think that still gives the ability for the auction price to increase if prices are not well known/rare pieces.

And if it is a seller well known on the forum, I think it can work extremely well.

I do wonder is if the seller isn't that well known but the piece is interesting, will people on the board hesitate to comment on the pluses/minuses of the watch if they are considering making an offer. But I suppose that can happen regardless of platform.