Not long ago I wrote that KDE 4 might produce enough changes to its look and feel to help Linux become more Mac-like.  At the time, Windows Vista seemed to be trying to move in the same direction.  Interestingly, someone has noted that Windows 7 now appears to be moving towards Linux's direction with the Windows desktop looking more like KDE 3.5.

The review
features screenshots and I must say, even though it has not convinced
me, Windows 7 is a step forward from Vista, at least as far as the GUI
is concerned.  Aside from the removal of some annoying Vista bells and
whistles and the new Peek and Snap window-management enhancements, it
is difficult not to notice the resemblance between Microsoft’s
much-touted revamped Aero and the excellent, now 3-years old, KDE 3.5.x.

Personally, I think Microsoft, Apple, and the Linux desktop developers have run out of ideas.  Any new innovation for these desktops seem to be ideas borrowed and improved from each other's desktops.  This is one of the reasons why I have lost my "wow" when it comes to operating systems.  In 2007, I wrote:

With PCs or laptops at my house now containing Windows, Linux, and
Apple computers, I'm a three-operating system household.  It dawned on
me that indeed "this is a frustrating time" for me when it comes to
operating systems for personal computers.  For all the "variety" of
computers we use in my home, they basically have the same features and
from a user's perspective the operating systems are really not all that
unique from each other.

It has been a very long time since I've really said "Wow, this is an
operating system I can't live without".  Yes, the Windows Vista "Wow" campaign
really overestimated users' impressions of Vista (it really was more of
a "Is this all there is?" campaign).  But be honest Apple and Linux
fans...when is really the last time you said "Wow" when using your
desktop?

This is why I think the real improvements to be made with operating systems is not the desktop.  Instead, I think it is in the area of performance and reliability.  Windows is currently too slow, OS X is too confined in its own hardware, and Linux stumbles too often.  It is no coincidence that both Apple and Microsoft are working harder than in past years to improve those things that users don't see in their next versions of their operating system.  Until something significantly changes with the hardware or IT culture there just is not much more to be done on the desktop.