[cooldeal]

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.

[wvenable]

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.

[cooldeal]

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.

[wvenable]

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.