There is also currently no neutral AH- gadget is gone, as is booty bay.
Prices fluctuate pretty rapidly from week to week, so a history might not be as much use as you would think. For instance- last week, silk was down (everyone was setting their buyout prices low), so I bought about 12 stacks for 20s apeice. This week, price was up, and I successfully unloaded all of them at 55s buyout prices. I've read others commenting on the trade boards about this phenomenon, so I think it happens with all kinds of things.
Proxy bidding would be a godsend for buyer and seller alike.
While there is no history button, there is often more than one of whatever you want for sale. For examle- as I type this, 10 people are selling stacks of 20 copper ingots. You can get a good concept of what the current value of something is by just looking at what people are charging for it.
One other thing I should probably mention is that when you put an item up for bidding, the game provides you with a suggested reserve price based on what the item would sell for at a vendor. In most cases, I use this. If it is an item that is especially well suited for a class (say a shield that has stamina and strenght bonuses- perfect for a warrior), then I may bring up the cost a bit. I always set the price at something that I think is reasonable, as I would rather have a large quantity of good trades than a few trades where I lucked out and found someone who was willing to pay me too much for whatever. I think I make more money overall doing that, and it is nice knowing that the buyer and the seller are both happy with the deal.