According to the Yahoo Alpha blog, the service adds elements of personalization, RSS functionality, and the ability for users to share their results with friends:
Whilst aggregating feeds on one page is nothing new, we wanted to take a federated search concept one step further. With this beta, we have introduced personalisation elements that not only allow users to customise their view, but also to add their favourite search service (at least those who syndicate their search results via OpenSearch RSS).
We also decided to add a sharing element for logged in users of the site. Now, if you decide to share your personalised url with others, they can view and effectively use the search configuration you have developed.
The screenshot of Yahoo Alpha, which sports an AJAX interface, is below:
Here are what the SERPs look like. Oddly enough, the Sponsored Results are actually hidden unless you click on them!
So far, it's really open to the "Australian community," but that didn't stop me from getting a sneak peek (or you either). Check it out and then join the discussion at WebmasterWorld.