It works, the first time you load an area which was never cached before can take a long time though.

I used it for a train ride from Amsterdam to Paris and I didn't pre-cache the map before I left so it was using the slow connection all the way.

It drew the map at a high level. If I tried to zoom in on any area for detail, it took awhile to download that portion. So that means it displayed the outlines of the area but not borders or city labels unless I zoomed in and gave it a chance to download more data.