For most at-home end users Linux has been good enough for years. Most of these people only use two applications: a web browser (through which they also get web based email), you have a choice of many with Linux; and an office suite (word processing and spreadsheet) that Open Office does excellently. They will not need to use the command line.
Other needs: printing is easy via CUPS; system updates easy; package installation easy; Gimp OK for simple image editing; music playing - well supported; SANE does scanners well.
It just needs someone to do the installation and provide a little initial hand holding and most people then just get on with it. Their main problem is fear of the unknown before they start -- so do your bit and offer to hold peoples' hands.
Yes: there are always people who need something special that you can only find on MS Windows or a Mac; but I am talking about the 80% of home users.