It's just plain faster
One of the biggest complaints about Vista was its speed --- even with Aero Glass turned off, users said it was sluggish. That's not the case with the Windows 7 beta; it's quite speedy. I have Windows 7 installed on a laptop with a 1.83 duo core CPU and 1 GB of RAM, and it's plenty fast, certainly faster than Vista was. And if I turn off Aero Glass, it's exceptionally responsive.
The new taskbar is nifty
The Windows 7 taskbar (see it in action, below) is somewhat like the Mac OS X Dock --- after all, why not steal what's worth stealing? It does double-duty as an application launcher and windows manager. So if you have Internet Explorer open to three Web sites, for example, when you hover your mouse over its stacked icon, hover your mouse over the stacked icon, and you'll see all three open tabs as thumbnails just across the top of the task bar. Hover your mouse over any of the thumbnails, and your entire desktop is taken up by that open window.
You'll want Aero Peek
Aero Peek is a nice addition to Aero that lets you "peek" behind any open window to your desktop. It's far better than Show Desktop icon that lived on the Quick Launch bar in previous versions of Windows. Aero Peek lives as a small, rectangular area just to the right of the clock at the right edge of the task bar. When you have windows open and you mouse over the Aero Peek rectangle, all of your open windows disappear, and you see through to your desktop. But you don't see just the desktop -- you also see the outlines where each of your open windows would be.
The Jump List will improve your productivity
Right-click an application's icon in the taskbar or click a small arrow next to its icon in the the Most Recently Used application list, and you'll find the Jump List. (See the screenshot below.) You'll see a history list of the most recent open files -- or Web sites, in the case of Internet Explorer -- as well as a variety of tasks associated with that application. It makes finding files and performing various tasks much faster.
It tames UACWindows Vista's User Account Control is almost universally reviled, and with good reason. It's annoying and intrusive, and can make using Vista an unpleasant experience.
However, it also makes Windows safer. In Windows 7, Microsoft has finally tamed UAC and still kept it useful. You can now customize it so that it will only rarely pop up a prompt. It's a very good balance between security and usability.
It has a real backup program
The backup program built into Windows Vista was one of the most worthless applications that ever shipped with an operating system. The one in Windows 7 is actually useful, and one I'll use all the time. With it you can choose individual files and folders you want to back up, something that wasn't possible in Windows Vista.
Search and file management are much improved
Earlier versions of Windows practically forced to organize all of your files and documents under the Documents folder in your user account. Not so with Windows 7. Instead of organizing your files and folders in a Documents folder, there is instead an overall Libraries folder, under which separate Downloads, Music, Pictures, and Videos areas can be found.
You can now include folders from other locations on your network in your Libraries. For example, if you have three PCs, and you would like to be able to see all of your work files from all those PCs in one location, you can drag them to your library. Those folders will still live in their original locations but will also show up in your library
As for search, from your Windows 7 machine, you can easily search through other PCs on your network. Place the folders from another PC into a library, do a search on that library, and you'll search the other PC's folders
Also, search results are easier to scan, and offer more information for each file. It's also much easier to filter searches using file name, author, and file type, because those filters appear just underneath the Windows Explorer search box when you put your cursor into the box.
The upshot? When Windows 7 comes out, it'll most likely be well worth the upgrade. For more details about Windows 7, see my two reviews: Review: Windows 7 Beta 1 shows off new task bar, more UI goodies, and Windows 7 in-depth review and video: This time Microsoft gets it right.