In my opinion, ListPicker list items are unacceptably small tap targets; certainly their height is smaller than the minimum size recommended by the style guide Microsoft published, and fact that Microsoft has taken to presenting the list full-screen in a much larger font suggests that I am not alone in holding this opinion.
I would like to use this full-screen big-font presentation in my own UI designs. I have tried specifying a DataTemplate (as a static resource) but it didn't seem to have any effect, although I'm pretty sure it is processed because when I made a typo in the resource name the compiler complained.
I was using ListPickerItem objects for the items. This works until there are enough items to trigger Full mode and then it barfs.
If I import the System namespace and use String objects, everything's hunky dory. Supplying a DataTemplate and binding to something also works.
I think I have found a bona fide bug, but one with a trivial workaround: don't use ListPickerItem.