I suppose it's similar to Yahoo's buy price, which
I like because it does discourage crazy bidding 
and allows someone to get an item faster.. 
(Though someone could place an insane buy-now/buy-
price, too O_o') I don't know the details, though 
I was told the "buy now" option only appears for 
the first bidder. Also, I hear that eBay will 
probably charge a fee for it later (no surprise 
-_-). Whether or not it's a good/bad thing for the 
auction principle, I don't know and don't really 
care for my purposes as I tend to use a buy price 
on my Yahoo auctions anyway. ^_^