I wouldn't consider the Start Menu a major change, because it's not new, but a combined effort to merge the previous (Windows 7 and before) and the current Start Screen (Windows 8 and 8.1) into a single OS feature. The virtual desktops is probably one of the more welcomed changes for some users, however, I wonder what the Linux community think. Windowed Modern Apps is an interesting take on bringing Modern to the Desktop, unlike before it was either one or the other, even with App Snapping, it never felt like "One" experience.
I do hope that Modern UI Apps become more feature-rich so they can be used to replace some desktop apps. For example; Skype for Windows Desktop vs Skype for Windows.