Min Ming Lo has published a good initial comparison of the OS X Yosemite beta UI compared to Mavericks:

Apple revealed a sneak peek into Mac OS X Yosemite earlier this week. Not surprisingly, Apple updated its desktop OS to match iOS 7’s design language. The new OS X now embodies a brighter and flatter styling, coupled with icon updates, font changes, and translucent materials. Here’s a quick look at the visual design changes in Yosemite and my impressions of them.

Clearly Apple has a lot of work ahead to polish Yosemite before the final release, but I’m a fan of the new direction. And, unlike others, I’m glad to see a happier Finder. Who doesn’t like smiles?