On March 27, 2012, Google will make the new look for Gmail the permanent, and only, look for Gmail for all users.
The new look for Gmail has been available for several months now and for those of us who adopted it early on, the old look is a distant memory. However, if you have been clinging to the old Gmail display format for some reason, your time in the sun has come to an end.
The old look
This is the old Gmail look that is soon to be a part of history
On March 27, 2012, Google will make the new Gmail look the only Gmail look.
The new look
This is the new Gmail look - not that much different really
As you can see in the screenshot comparisons, the new look is a little cleaner and generally easier to navigate. I don't think many users will object to it, but you may want to give everyone in your organization the heads up that there are changes coming - that is if you haven't already.