I had a Treo 650 before I had an iPhone and always thought of the iPhone as an evolution, not a revolution. The reason that I switched was that I was mainly using Mac OS X on the desktop at that time, so using iPhone OS (as it was called then) as a companion was kind of a no-brainer.
However, in hindsight, even more than Palm OS I actually miss Pocket PC.
I don't agree actually, having used various mobile devices, including a Palm III, Jornada 548, Visor Pro, and the Samsung Blackjack 1 and 2. Sure, they had some nice features (and gimmicks) but the ease of use outside of the basic PIM apps left much to be desired, the screens were mediocre at best, and mobile web browsers on Pocket PC and the Blackjacks were at best good only for checking news/weather. I still remember watching the iPhone keynote livestream and being absolutely blown away, only settling for the Samsung because my parents didn't want to splurge (probably for the best, as I lost the 1 and got a 2 as the replacement). In my second year of college I lucked out and a friend sold me her iPhone with a shattered front glass, and with a bit of surgery I repaired it and used it until the launch of the 3GS. After that I never looked back (well, now I collect vintage PDAs so that's not /entirely/ true heh).
Don't get me wrong the other devices were (and are!) fun to tinker with, but for something I use every day and depend on like a phone I just want it to work.
Of course web browsing was “inferior” compared to an iPhone, but the Jornada also got released 7 years earlier. You could argue that the web itself wasn’t really useable beyond checking the news and weather back then (not saying it is today, but that’s another story).
Also keep in mind that iPhone OS didn’t even have downloadable apps initially.
However, in hindsight, even more than Palm OS I actually miss Pocket PC.