Most of the applications were far more advanced that what you find on the iPhone and Android (at least until recently after pouring years of development into iOs and Android) - there's no way you can disqualify the PDA apps as being "not really interesting", and you had access to phone functions through the development environment. Of course, there was no accelerator, no multi-touch screen, no GPS, so a number of functions were missing but the software part was advanced and very capable. That was when the iPod was big as a brick and could not run any application, for your information.
What platform or apps are you talking about? I remember WinCE (Compaq Ipaq) which I hacked to run Linux, but I only ever had the PDA form of those, and it was essentially a small laptop (ipaq + cradle + 4GB HDD on CF card + metricom ricochet modem), and the Handspring (PalmOS) things. Nothing on PalmOS was particularly advanced. WinCE did have a lot of desktop-app-ports, but I didn't know anyone actually used them.
I used applications on WinCE - I had a Toshiba PDA. I cannot remember all the application names, but SPB was one of the key developpers for the platforms and their organizer/calendar/scheduler apps (Spb Calendar if I remember correctly) was much better than what you could find on iOS or Android until recently. There were also applications that could open and edit actual word documents and excel sheets (forgot the name) which worked pretty well for tweaking existing files.
The main drawback was the lack of a good browser - these were the days before firefox/chromium so there were no real alternatives out there.
But I had Skype running to call people YEARS before any smartphone could do it. Smartphones were just catching up to what the original PDAs were capable of doing, basically.
