The QuickGrid plugin has been modified to support labels, which you can edit to include a description of the grid settings. A sample is provided which shows empirical conversion to inches if 1 AC3D unit is equal to 1 metre.
http://bellsouthpwp.net/a/t/atomicd/...quickgrid.html
This update is handy if you're used to working with empirical measurements (inches, feet, etc), or if the scale of 1 unit to 1 metre does not hold true for your document.
NOTE that this is only a label that provides a reference for your grid settings - no functionality has changed here.