He points out that working in a multiuser environment lets you troubleshoot issues without mucking up your current system setup. When trouble arises, just hop over to your test environment and tweak to your heart's content.
Business users can create a presentation profile that lets them give a presentation using their Mac without worrying about their co-workers seeing photos from their weekend getaway.
You can read Griffiths' full article on Macworld's website. There are applicable tips there for the average user, business users and even gamers.