A list with two lines for each item, with height for each item correctly adjusted
The result that occurs instead:
A list with the separators and items misaligned
If you go to the 2.0 docs and try the same thing on the same example, everything looks as expected.
I have not looked very closely into the reason for this change in behaviour, but I can see that the rendering of the list items have changed significantly from 2.0 to 2.1. Amongst other, the position for each .x-list-item now is absolute, which leads me to think that there is some kind of computation of the top positon of each item.