I had the iPod Touch and iPhone relatively early (well, much earlier than the general population). I don't remember Shazam being important at all, I think I only discovered it a few years later.

What blew pretty much everyone away that I showed it is how incredibly smooth web browsing was (remember, there were no apps on the original iPhone and even after that it took a little while for apps to really take off). Most smartphones at the time had clunky resistive touch screens or even little joysticks to move a mouse pointer. With the iPhone, you could scroll with your fingers and it was butter-smooth (at least for the day). The iPhone was a game-changer because you had a device in your pocket that you could browse the web with and it was at least as easy as on a desktop, if not easier.

Just for comparison, this is how you browsed the web at the time on probably the most iconic smartphone at the time (Blackberry):

https://www.youtube.com/watch?v=5NuQrjBIofo&t=6s

and on an iPhone:

https://www.youtube.com/watch?v=euNlVt60hwk

I second this - for me, it was the browser - it was usable with normal websites.

It was SO much better at browsing than my BlackBerry at the time. Though I vastly preferred all messaging on my BlackBerry.