Huh what? The UI has been pretty much the same since Windows 95. Meanwhile OS X changed the scrolling, and lost scrollbars and a whole bunch of other changes in Lion that people aren't very fond of.
The public seems to have gotten along very well with the Windows 7 UI over XP without much, if any re-learning.
Vista was different because it actually changed the security and driver model, breaking a lot of hardware and software. I haven't seen too many complaints about the actual UI.
By "everytime they iterate", you mean Windows 3.1 to Windows 95(very well received) and Windows 7 to Windows 8(desktop mode is exactly the same) which is what, twice in 20 years? Maybe thrice if you count the taskbar changes in Windows 7.
Vista's UI is terrible but it wasn't until Windows 7 that I figured out why: Vista is the half-complete transition from the XP UI to the 7 UI. As such, it's got loads of issues and inconsistencies.
I know the moving control panel, network properties etc. led to a lot of annoyances, but in terms of the actual window handling, taskbar, start menu, how was it terrible?
The search box on the start menu was itself a huge leap over XP. That was the single big thing I missed in XP.
Far enough, anything unchanged from XP isn't terrible. And the start menu search box is a big improvement even if the rest of the start menu seems worse.
The public seems to have gotten along very well with the Windows 7 UI over XP without much, if any re-learning.
Vista was different because it actually changed the security and driver model, breaking a lot of hardware and software. I haven't seen too many complaints about the actual UI.
By "everytime they iterate", you mean Windows 3.1 to Windows 95(very well received) and Windows 7 to Windows 8(desktop mode is exactly the same) which is what, twice in 20 years? Maybe thrice if you count the taskbar changes in Windows 7.