In the following example antialiasing has no effect:

import QtQuick 2.0

Item {
    width: 400; height: 400
    Rectangle {
        width: 100; height: 100
        anchors.centerIn: parent
        color: "green"
        antialiasing: false
    }
}

Ideally it would be possible to turn off antialiasing.

Currently reading the antialiasing property also does not always reflect the true state of antialiasing (i.e. if the user has not explicitly set it to false, reading the property does not return 'true' if there is a radius).