When we got our first peek at Windows Live wave 3 back in 2008, what we saw was a preview of what was to become the Windows 7 user interface. That is, it featured the light blue, buttonless toolbar type that later showed up in Windows 7, and one app, Movie Maker, even utilized the second-generation "Scenic" ribbon, also used by Paint and WordPad in Windows 7.
Most of the applications have adopted a new look and feel that includes a new type of toolbar. This look and feel mimics that of the upcoming Windows 7 Explorer shell, and for a reason: Microsoft is removing a number of bundled applications from Windows 7 and making them part of Windows Live instead. But the company also wants to ensure that these downloadable applications look at home in Windows, thus the common look.
So Windows Live Wave 3 is our first glimpse at the UI Microsoft is supplying with the next Windows. Early reactions are mixed: The new toolbar type dispenses with icons almost completely, mostly using instead textual buttons that are Spartan and bare-looking in appearance. I'm OK with it, to be honest, and I suspect the goal here is to take the attention away from the window chrome so you can focus more on what you're doing.
In Windows Live wave 4, the UI is changing yet again. This time around, virtually all of the Essentials pick up the Scenic ribbon. Which is interesting, when you think about it, because that ribbon version is now actually older than the ribbon used in Office 2010. (The first generation ribbon appeared in Office 2007. The version in Office 2010, which features the File tab, is the third generation ribbon.)
One other thing that pops up in these apps is a prominent use of the Segoe family of fonts that's also used in Windows Phone 7 (and related products like Zune). You can see this in Messenger most clearly, which in its new full view takes on a decidedly Windows Phone 7 "Metro"-like look and feel, with a panoramic view of your social networking updates. Is this a peek at the UI we're going to see in Windows 8?
It's not clear, honestly. Messenger has always done its own thing, of course, and this could simply be a one-off thing. But this font shows up elsewhere in Essentials too, and given how clean it is, and what I assume would be a desirable tie-in with the phone stuff, it could make sense. I'd love to see Microsoft use more of a Metro look and feel in Windows 8.