So some screenshots have surfaced of the latest Leopard build, showing the death of Brushed Metal and the introduction of a more itunes like interface, but with the old Aqua buttons and form widgets. I think Leopard's final UI won't look much like this. Here's my rationale. First, look at the current Leopard build. Notice how there aren't any brand NEW UI assets that aren't just a cut-and-paste job from Tiger? It's just a mish-mash of Tiger's assets. Not a single new asset. That screams of this current UI just being placeholder for something much bigger, and much more different. Next, take a look at the iPod's current UI,. Since the iPod UI so closely mirrors Tiger's UI, it makes sense that Apple would position their next-generation iPhone's UI to mirror their next-generation OS's UI - Leopard. I feel that Apple will want to maintain a visual consistency between their next generation products like they have in the past, and I feel that we have already seen some key elements of this new visual style. If you look closely on the iPhone keynote video, you'll notice that during the Safari demo, the form widgets look drastically different than the form widgets in Tiger. Instead of bright blue glossyness, they have replaced it with a glossy black surface. I think this dark, smooth black UI design is the direction that Leopard is taking. In the State of the Mac Union address at WWDC, Andreas Wendker showed a rough concept for a next generation Finder using the brand new Core Animation interface frameworks, that happened to be completely black. (They didn't call it a "Finder" concept though though, they just called it a way to view files.) Also it's interesting to note how scrollbars work on the iPhone. Gone are the big chunky scrollbars that take up 20px on the side of every window. On the iPhone, scrollbars are very slim things, single color 2D vector shapes that are normally completely invisible. They only fade in only when a scrolling action is performed on a page, and I think that if they carry over to Leopard, they will fade in when your mouse is in close proximity to the side of a page. You could just whip your mouse over to the side of a page and have a "mouse proximity sensor" kick in to get your bearings or jog to the middle of the page instead of scrolling. The "cloud" which would activate the fade in of the mouse could be fairly large. To indicate that there is page overflow occurring, the scrollbar could fade in as a page loads and grows, showing the user that the page does have extra content on it. So basically the scrollbars are out of your way until you need to scroll. Most people scroll with their scroll wheels now anyway, so they would be great at showing you your place in a page and then quickly fading out and getting out of your way. Basically that's how I see the 10.5 / 10.6 evolving in the future.