The biggest problem with the Steam trading system is that you both needed to be online at the same time. Sure, it added to the tension of the trade, and there were times when I pretended to be a high-level broker sitting across from another high-level broker and we were sweating, but that sort of pressure does tend to squeeze the bowels. Because of that, most of my Steam Trades took about an hour as each of us had to keep running off to make plopsy. Well that's no longer a problem! The latest update allows you to send trade requests without requiring the recipient to be online at the same time. And you can now send them via the website, too. It means I can trade and strain at the same time.
The other thing (that I realise is quite annoying now that I think about) is that trades were a give-and-take scenario: you placed your items into the trade window, the other player did the same, and you have to accept the trade. For a certain 'what have ya got?' trade that's fine, but if you know what you want you can now just package up an offer and send it off. Basically it's 'You have this and I'll give you this for it'.
As is the way of the world, someone has detailed this on YourFaceInATube.