I would love to see this ability: when you type in the bid price, it automatically makes your buyout price the same. You can then change the buyout price if you want, or leave the two equal and post from there. It would save SO much typing on our part. And most professional AH'ers make the buyout and bid price the same anyway.
Perhaps the functionality could be created such that if either field is blank, an update to the other field copies input. That is to say, an update to the buyout fields will replicate to an unedited bid field and vice versa.