Usability seems to have been a major issue, as can be read in a report by Thomas Crampton in the International Herald Tribune:
To Neuf, the issue came down to the difficulty that first-time computer users experience in dealing with Windows.
“Nearly 80 percent of all current customer calls relate to problems with Microsoft Windows,” said Frédéric Charrier, manager of the Easy Neuf project. “We decided it was easier to build our own platform to limit potential problems.”
“Our promise of customer service forced us to conceive everything from the consumer perspective in order to reduce calls,” Charrier said. “This starts with the instruction book containing many photos, goes as far as the simplified computer interface and goes down to a redesign of the keyboard.”
Also, the software is entirely open source.