I'm also going to give kudos to the new auction system. The only feedback that I have is the penny increments, but I've stated that before. I've used this system to sell and purchase eggs and so far haven't run into any issues. I love that it hits your pm box with a pm when an auction is over for both the buyer and seller.
We've also had some people post a $0.00 BIN item for sale in the proper BSA listings and in the subject and body say "Trade: my XXXX for YYY"
Then the person who has the item and wants to trade can click "Buy it now" and then you can do the trade. I'd actually suggest this over "wanted to buy" because it will attach feedback to the trade.