I don't think that the current text field with the Old/New is as useful as it could be. I think that probably old and new should be fields in the database with just the value. Maybe this could be a configuration option, "Store audited values as separate fields".
The issue is that I want to be able to do "retrospectives", i.e. what was the state of the database at a certain point in time? To be even more clear, I would like to query "What was the state of the database on July 1, 2010?". The objective will actually be- What did we expect to happen as of July 1, and how does that compare with the next round of updates?" Formulating those queries might be a little tricky, but we can deal with that once this suggestion is implemented.
OK, I think this is pretty obvious and minor, because you obviously already have the trigger for on update.
Thanks for this feature as it currently exists, BTW.