I did a search for this and it seems strange that there doesn't appear to be a post previously, but nevermind.
Under the 'Units' tab in the document settings, it would be great to be able to specify a separate unit for volume. I get that most american designers will work in inches and therefore this converts neatly into cubic inches, but under the metric system this results in volumes being listed in cubic millimetres, rather than the more useful litres or millilitres.