For some reason the controls do not support the DataForm mode.
I had to catch the ContentLoaded event and manually set the Enabled state of each Telerik control.
In case you havnt used it:
isEditing = !(ElemForm.Mode == DataFormMode.ReadOnly);
RadGridView crusherGrid = (RadGridView)ElemForm.FindNameInContent(
) crusherGrid.IsEnabled = isEditing;
My other problem in the OP was with the appearance compared to the non-Telerik controls. RadMaskedTextBox did not work with MaskType="None" at that point, so Microsoft text boxes mixed with Telerik controls was not a good look.