I don't think a casual user would in many cases even be able to tell the difference. I mean you have a desktop with some icons which most of people only use to start the browser which is absolutely identical in both systems.
You have a start menu with other programs and you have a task bar which shows the open programs and some status icons and a clock.
It is really not that different. Most people just start a browser and go on Facebook or eBay or whatever, use a simple word processor for the daily needs. I don't think they would be able to tell the difference.