With Windows 7, Microsoft has given the UI yet another complete makeover.
What does the overall appearance remind you of? No hints, figure it out on your own. :P

• Flip3D, that Exposé ripoff, no longer has an icon in the quick launch. However, pressing Win+Tab will still activate it.
• The quick-launch as a whole is now gone.
• The taskbar is quite different.
• Show Desktop is now a sleek-looking button on the right side of the taskbar.
• The Sidebar is gone as well.

The webby Personalize dialog has been slightly enhanced to now display a few images as well as the properties.

The start menu is mostly unchanged, however the old Internet and E-mail options that used to be pinned to the top are now gone, as is the Search option.

If the overall appearance of this new taskbar doesn't remind you of the Dock in Mac OS X, then you weren't paying close enough attention.

The new task bar takes the quick launch and merges it with the open window list. By default, there are icons "pinned" to the taskbar for Internet Explorer, the Explorer, and for Media Player. In this example, IE has been unpinned (like it should be) and the Calculator and Paint apps have been pinned.
Instead of placing a new button on the task bar for each open window, all buttons for each program are combined into one, and the icon changes to look like a button. Right-clicking the button/icon opens up a menu allowing you to perform basic operations.

Vista introduced preview windows for open windows, however in Windows 7, if you have multiple windows per program, mousing over the button displays a preview of all the open windows at once. Mousing over one causes all the other windows to become transparent and brings the one in context to the front.