Windows 7 tones down the number of "are you sure?" security alerts from the User Access Control function -- and even lets you control the nag level. However, some experts view this nag-reduction functionality as a sure path to compromised security.
Windows 7 sets in place a multicore foundation that should matter increasingly as multicore PCs become the norm and applications are written accordingly. You won't likely experience that benefit for some years, but XP could never get you there.
The new Windows 7 task bar -- even if it is "inspired" by Mac OS X's Dock -- and its companion Aero Peak feature (available only if you have the right graphics hardware and driver) -- inspired by Mac OS X's Exposé feature -- go a long way toward making it easy to run and navigate among multiple applications, essential for day-to-day operations. There are other UI improvements that -- once the applications you use are upgraded to support them -- are also compelling, such as jump lists (contextual menus on steroids) and task bar animations.
For IT, Windows 7's support (in some versions) for a single image in multilingual environments, as well as management capabilities such as better encryption setup and management through BitLocker and AppLocker, is welcome. Note that many of Windows 7's management and networking improvements, such as BranchCache and DirectAccess, require that you also upgrade your back-end Microsoft infrastructure, such as by using Windows Server 2008 R2.
Finally, the application incompatibilities that bedeviled Vista users seem to be largely handled by Windows 7.
Where Windows 7 falls flat But Windows 7 has some real drawbacks that temper any passion I might feel for it. The biggest downer is the new UI. Yes, the Aero "glass" stuff is cool, assuming you have compatible video hardware and drivers, but that eye candy wears off pretty fast. What I just can't accept is the contextual approach of the UI, where Windows hides most functions from you and guesses as to what you want. It makes me work too hard because Windows rarely knows what I'm looking for.