Have No Fear
Are you looking forward to upgrading to SharePoint 2010 but afraid of what might happen to your day-to-day operations during the transition?
Have no fear. One of the most talked about features in the upcoming release is the ability to upgrade to SharePoint 2010 but keep the older interfaces.
Using this setup, two environments operate in parallel. One is a test environment using the new interfaces for training. The other uses the old interfaces for regular day-to-day work. Once training is complete, the new interfaces can be installed across the server.