Palm Treo 650
I previously used a Samsung i500 before I purchased a Treo 650. It was a great phone, but lacked the usability of the Treo for sending text messages and emails.
I purchased the 650 after missing 10 calls one day during committee meetings. I decided I needed to be more accessible to my clients and business partners. The Treo has been a great tool for that.
I have a friend who has two Treos so he can talk on one and type on the other.
The 650 seems to be much more stable than the 600, has a better screen, built-in Bluetooth and a better camera. I'm holding off on the 700w and 700p, though to see the experience of others.
My Treo has been relatively stable and had not lost data or required a hard reset until I did a firmware upgrade a few days ago. Syncing my Treo is really simple now that I have a laptop with a Bluetooth card. It does take a while now that I have a number of files and photos on my Treo.
All in all, the 650 is a great product that does much more than I'll ever use it for, but makes the things I do often much easier.