I've noticed that some WinRT apps that are built on C++/C# (not HTML/JS apps hosted in Internet Explorer) have non-functional scrolling if you use a laptop with a Synaptics touchpad, and try to use either one or two finger scrolling in the app's main client area. Example apps are Tweetro and Cocktail Mix.

Scrolling does work without the Synaptics drivers, when Windows treats the touchpad as a generic mouse, so something is clearly broken in the Synaptics drivers. I've tried the OEM set and the ones from their site without success.