Why are PDAs suddenly that weird uncle you never talk about and only see at birthdays? Because they ultimately failed in the market. There was a reason that the Blackberry and Treo type devices became popular. They worked better than the early touchscreen devices. Those early deficiencies left manufacturers gunshy about creating more touchscreen devices. It was combination of hardware issues (resistive, single touch)…
Yes. All my Blackberry toting friends were pooh-poohing the notion of a virtual keyboard, and now, the loudest critics among my peers have totally jumped ship, singing a different tune.
Regarding PDAs being that "weird uncle"...
I've had just about every PDA form-factor going back to the clamshell Sharp Wizards (which had these weird touch panels) in the late 80s to the Newton Messagepad to Windows CE, Palm and eventually Windows Mobile. The iPhone is the first "PDA" that I actually consistently use. The way you used the core features of the phone (contacts and calendar) were vastly better than anything I used prior.
Of course, I would have no problem using any "post-iOS" phone OS, which would include Windows Phone, Android and Web OS, but there really is something about the first iPhone UI that made it special. Is it as special today? Not really, but in 2007, yeah, it was pretty revolutionary.