Flickable lists in QML are unusable. As is bauhaus the visual QML editor in Qt Creator. It seems clicked or released events do not fire from the mouse under Qt 4.7 for Cocoa.

Compile Qt Creator master with Qt Master.
Open creator and import examples/declarative.
Open dial/dial.qml
Switch to design mode.
Without additional clicks you should be able to click on the dial, hold and drag it. You cannot the first time because of this bug and it renders the visual editor unusable.