Earlier quoted context omitted.
Redesigns of a heavily-used UI are always "usability disasters". People spend many hours perfecting their workflow in one environment and FLIP THEIR LIDS when someone changes it. It's not a rational thing (nor, frankly, an unjustified one). What surprises me is that we haven't figured this out yet and rehash the same flame war every time. The desktop environments show this best: c.f. Gnome 3. Also Gnome 2. And Gnome…
You're begging the question. If we take what you say is true every redesign is good, which is patently false. A perfect example is the Office Ribbon UI, an unmitigated disaster. Also putting Vista in your list there, mmmmmm. Wasn't exactly a great redesign was it. The Google redesign is also pretty much a disaster.
use ms office daily, love the ribbon.