My sense here is that Microsoft has been criticized so often for security vulnerabilities that it decided to club users over the head with its new operating system-in-lockdown-mode. It reminds me of the early days of HTML, when Web designers everywhere suddenly seemed to discover the blink tag -- and sites everywhere began blinking at users. In a short while, all that blinking became distracting, then annoying, then finally ended as people got fed up. My sense is that a lot of users will get tired of UAC very quickly and do whatever they can to shut it off. That could leave them vulnerable to genuine threats and obviate the enhanced security Microsoft is so proud of.
I'm more enamored of Vista's Flip 3D feature, which basically takes all of the open windows on your desktop, stands them up on end and stacks them in a way that you can cycle through to the one you want to use. It's similar to what Apple's Expose does. In Mac OS X, all of the open windows are arranged in a two-dimensional way that makes it easy to see what's in each one. But it's not as visually appealing.
Both do pretty much the same thing; Vista's method wins on aesthetics.
Gadgets can be run multiple times, both on the desktop and in the Sidebar.
(Click here to see larger view)
I'm less enamored of Vista's new sidebar feature, which allows small gadgets to run on screen all the time. These are useful little apps like a clock, CPU meter, currency converter, a weather window and stock ticker. You can run multiple instances of each gadget, plopping two clocks set for different time zones right on your screen. Gadgets generally sit in the sidebar and can be localized and customized -- moved to the desktop or made transparent, for instance -- or turned off altogether. They perform many of the same functions as widgets in Mac OS X, except that widgets are called up with a key combo and float onto the screen in front a user's other windows. They don't run in the OS X dock, and you can't move them to the desktop without some third-party intervention. Maybe I'm just used to calling up widgets on my MacBook Pro with a quick keystroke -- and dismissing them just as quickly -- but I find widgets easier to use. They don't get in the way and aren't there when not needed. Gadgets, if they remain in the dock, take up screen real estate. Or if I move them onto the Vista desktop and hide the sidebar, they sit behind the windows I'm using in the foreground. That means moving the windows around to find the gadget and check whatever information it provides. While gadgets can be set to remain on top of other windows, you then have to move the gadget around to see what you're working on. In other words, the gadgets are useful tools that get in the way -- meaning many users may well turn them off.