Zi makes progress with Qix
Zi makes progress with Qix: "Virgin Mobile reported a 33 percent increase in ARPU from devices equipped with Qix"
The last time I heard about a rise in ARPU that significant in relation to handset UI was in 1999/2000, when I remember being told that Nokia users generated 2x the text messaging traffic of other device owners... I guess it's (sadly) rare to see such an overt and documented link between decent UI and revenue.