Well, for me, the biggie is that for mobile devices, most of the time people use them in short bursts, or in situations where it is inconvenient to sit down in front of a keyboard. As such, most mobile apps concentrate on having very simple interfaces (mostly touch related) for rather limited tasks. On a desktop machine however, you can take lots of time and use a variety of extravagant input devices.

QML is _great_ for creating a beautiful touch-based interface to an app. However, if you're trying to write a large application that involves complex interaction with the user, particularly if you want to use lots of different windows and lots of menus, buttons, and fields for interaction, the Widgets system still has the advantage in being able to quickly and easily setup and manage large, complex user interfaces. (And the widgets integrate much better with native Windows, OSX or Linux UIs than QML does.)

Well, I did start to work on transitioning some of my existing code to QML, to make it ready for Sailfish for when I received my tablet. Which was scheduled to happen back in July... But for now, I've been working on other stuff. I'll come back to Sailfish when (if?) I can ever acquire a piece of hardware that actually runs the OS...