In vpx-statistics -> overview of diskspace used, you see an overview of diskspace used per container per application. The amount of diskspace per application is specified in the 'client applications' section. However in the statistics there is no link to the diskspace available.
When you happen to run out of diskspace, you don't get a notice on the page which informs you about diskspace usage. That's odd.
What do you think about a visual similar to iTunes which shows total capacity, free space and the space used per container. See the bottom of the screenshot for an impression: