Peter,
You're 'message key usage' sure helps to figure out what the context of words is. I think it's sufficient, though real translators will surely argue otherwise.
However, it would help to have 'Messages that are translated' ordered by 'Translated Message'. I think Marcin could need such a table too.
In the end, when everything is translated, one might need a complete ordered list (not per package) to edit the results of translations.
