It was both gradual and quick. Gradual because we had the Palm Pilot 10 years before https://en.wikipedia.org/wiki/PalmPilot https://en.wikipedia.org/wiki/Palm

It was both gradual and quick. Gradual because we had the Palm Pilot 10 years before https://en.wikipedia.org/wiki/PalmPilot https://en.wikipedia.org/wiki/PalmPilot Quick because I think the iPhone had the first capacitive touchscreen in that class of devices. Being able to touch with a finger tip instead of with a stylus or a finger nail is a big improvement for the UX. BTW it made it to the iPod only in 2010. The phone was subpar in Europe (2G and we have had 3G since 2003) but it sold really well because of the innovative interface and the look of it.