Navigation menus marked up as lists are much more accessible than menus marked up in tables or nested divs. One way to get a feel for this is to turn off CSS in the browser to see if the menu is still navigable. In Firefox, you can do this by choosing View > Page Style > No Style from the main menu. When we look at CssListMenus/Solutions/CssMenu-mixed-challenge.html in this view, here's what we see:
This is how a screen reader might "see" the page. Because of the logical structure, it should have no problem presenting it correctly.