I'm an IT tech in a school. I've been doing it now for about 5 months. It seemed at the beginning that I would have many opportunities to show off Ubuntu. A few weeks back I gave a copy to one of the students for the first time. Perhaps it's just a relationship thing. Then over the last few weeks I've installed it for one girl on her Dell Inspiron 8200. It was installed with Win XP and completely trashed with all kinds of things that made it unusable -literally- so I explained that while Ubuntu isn't windows and she can't run windows apps it isn't vulnerable to all these things that destroyed her Win XP install. While doing this a few other students took notice. They were so interested that they wanted to give a shot and I gave them a CD. I also installed Ubuntu for a fellow who only uses internet, email and MS word.
The deal I make people is this. After a few weeks I install Windows for them if they find that Ubuntu isn't working for them or if they simply don't like it. I explain what Ubuntu is and all the pros and cons. I try to make them aware of what they're doing in hopes that the right perspective will aid their transition.
Essentially these two cases are my test trials.
Both windows users who trash windows installs. Both can benefit from a system that has no spyware, virus' and malware. A system that essentially can't be trashed the way Windows can.