They're crap;
- Cannot text while walking
- Cannot text one-handed
- Cannot send picture messages
- Cannot use any IM client
- Cannot do anything with bluetooth
- Cannot use it as a USB modem
- Camera is rubbish
- No 3G or HSPDA
- Safari is buggy, and JavaScript implementation lacking
- You have to "hack" it to install software (on your own computer?)
God bless my Treo 750

It might be approaching two years old, but it offers far, far more OTB functionality than the iPhone, without getting onto the millions of applications I could install on it.