No, I use it to store the only value - a counter, which is incremented during the work of the app.
I use it's value to create a unique IDs for controls.
I just tried to put a line
console.log(sap.ui.getCore().getModel(<modelname>).getData());
into onBeforeRendering() and into onAfterRendering functions.
I can't read the data even from those, when just in onInit() I have set it.