For the VAST majority of home users, this is exactly the case. I converted my Mother-In-Law (67 years old) to Linux Mint and she loves it. She uses it for email and web to manage her bills.
Since she had a Vista machine that barely worked due to MS bloatware, she was thinking she would have to buy a new computer. I loaded the DVD, let her play with it and she loved it. Much better performance. So I did a local install and she has been running it for several months now.
I think since I use it every day at work for the product I work on, she thought it was a Geek tool with all kinds of CLI stuff. She wouldn't believe me when I told her, "It works just like Windows. A desktop, icons, Firefox...but better."
I still have a WinXP PC for a few things but I haven't booted it up in weeks.