I've noticed an error in 4.1 beta 3 relating to radio groups that was NOT present in 4.0.7. As far as I can tell this doesn't relate to any of the API changes stickied at the top of this forum.

According to the documentation, a radiogroup can accept a column parameter which can be either
a) A float
b) An integer
c) An array of floats/integers where floats represent proportional widths and integers fixed widths.

http://docs.sencha.com/ext-js/4-0/#!/api/Ext.form.RadioGroup-cfg-columns

When going with option c) the layout gets completely stuffed up (almost as if the columns were treating the floats as fixed widths).

Here is a screenshot demonstrating the problems under 4.1.0 beta 3 with FF.

extjs-radiogroup.png

Here is an example pulled from the radiogroup documentation (and modified slightly)

Code:
Ext.create('Ext.form.Panel', {
    title: 'RadioGroup Example',
    width: 300,
    height: 125,
    bodyPadding: 10,
    renderTo: Ext.getBody(),
    items:[{
        xtype: 'radiogroup',
        fieldLabel: 'Two Columns',
        // Arrange radio buttons into two columns, distributed vertically
        columns: [0.5, 80],
        vertical: true,
        items: [
            { boxLabel: 'Item 1', name: 'rb', inputValue: '1' },
            { boxLabel: 'Item 2', name: 'rb', inputValue: '2', checked: true},
            { boxLabel: 'Item 3', name: 'rb', inputValue: '3' },
            { boxLabel: 'Item 4', name: 'rb', inputValue: '4' },
            { boxLabel: 'Item 5', name: 'rb', inputValue: '5' },
            { boxLabel: 'Item 6', name: 'rb', inputValue: '6' }
        ]
    }]
});