First, they seem to default to only showing 7 items, even if the dialog contains more items. For example:

Now, the user can show all the items by resizing the window, but there is no obvious indication that any items are missing or that the window needs to be resized. Furthermore, this should really not require any user interaction since it the dialog should be properly sized to the text it was told to display. (As has been the case previously) I anticipate this causing a significant amount of user confusion, and I see no way to work around the issue ourselves.
Second, if they figure out they need to resize the window, but resize it such that a button (click area?) is touching the bottom, as in:

then the resize/drag handle at the bottom of the window is masked, and the user can't resize the window that way anymore. (Though they can recover using the bottom-corner drag/resize handles)
Third, the dialogs seem to wrap text very prematurely. Consider line 4 here:

which, even when resized to provide plenty of right-hand space, still wraps in the same spot:

(and note how the wrapped button 4 ended up cutting off button 9 again until it was resized)
The first issue (dialogs being too small to show all their text with no indication that anything is truncated) is by far the most critical.