It might not be too surprising given what we've seen from previous major releases of Skype, but thanks to the release of 7 for Mac, and the beta of 7 for Windows, we can see that the tradition holds. In addition to a revamped interface, Skype 7 has been treated to a number of enhancements that will simply make the experience of using it better. Well, hopefully.
One change, for example, is built-in thumbnails that appear in a chat after a photo is sent. Not only does this improve the look of a chat, it'll help you be able to pinpoint a certain time in a conversation much easier (assuming pictures were shared, of course). Further, if documents are shared, especially those from Microsoft's Office family, and PDFs, they'll appear as their document icon, rather than a preview like the photos. This is probably a good thing.
Perhaps the most useful feature in Skype 7 is a dual-paned design, which will allow you to keep the chat box right beside a video chat so that it can continue to be used. This implementation in Skype 6 is really truly awful, usually requiring fumbling around with icons to find the chat at all, so this is a major improvement.
Ultimately, Microsoft's goal is to make Skype for the desktop as close to Skype for mobile as possible, so users can feel at home regardless of which version they're using. This is fine enough, I suppose, but I'm of the mind that if an app is on the desktop, it shouldn't adhere to typical mobile design goals. It seems like every company disagrees with me lately.
You can grab Skype 7 for Mac via normal means, since it's an official release, while for Skype 7 for Windows, you'll have to head here and click the "Download the preview version now" link.