Agreed, especially the point about alternate justifications. Using a non-centered justification would make it easier to see at a glance which fonts are monospace, which would help a lot for, say, exploring programming fonts (my primary use for font viewers).
Ideally, the list-of-font-names would have some hint where the font fits on major dimensions -- either by the common practice of rendering the name in the font, or by adding small icons/notations for monospace/serif/script/etc.
