After using a P800 for a year or so I upgraded to a P900 last Jun. It’s a reasonable phone and a very good organiser, which is its main use for me: managing appointments, contacts, TODO lists and so on. The Opera web browser on the device is usable for keeping up with news stories from web sites whilst out and about. And there’s plenty of third party software available for storing and retrieving the info I need from day-to-day. Data entry via character recognition works pretty well: I find it much faster than T9 or traditional phone number-to-character text entry. It does need two hands ‘though: one to hold the phone and the stylus in the other.
The P900 also works as a GPRS data adaptor for my TR1, connected via Bluetooth.
My P900 is fine. I’ve played with a P910, which has more internal memory and a small but usable thumb keyboard on the back of the number pad flip. The only thing it lacks is 3G connectivity, which looks to be starting to get usable for my typical work/travel patterns these days.