[yftsui]

My experience with Windows phone around 2010 was exact opposite, very slow and clumsy. I recall I tried a HTC phone on WM 6.5, far behind iPhone 3GS

[mardef]

That was Windows Mobile, which was the end of the line of the old Windows embedded line vs Windows Phone, the brand new OS made for modern (at the time) smartphones.

WP7 was the first of the new OS

[kcb]

Windows Phone 7 was another OS. Windows Phone 8 was the next totally incompatible OS just couple years later.