The main difference from the current Yahoo home page is that users can now customize the page with widgets/apps from third parties. Some apps have been pre-created by Yahoo and others. And others can be added as well, Yahoo will make the app based on the URL you supply (they don’t say it needs RSS, although I’m not sure how they create it on the fly without it).
The key change, besides personalized content, is the removal of the tons of links to scores of Yahoo services. Most people only use a handful of those services, says Yahoo, so it’s better to let users decide which ones are present and take up screen real estate.
Yahoo also says they will be letting users sync up the customizations between their mobile and desktop versions of Yahoo starting soon.