Treo might still be good choice
Even if you only use your cellphone occasionally, you might still find a Treo useful. I have a Treo 600 and I woud be completely lost without it. Once my Treo 600 no longer functions or sometime after the Treo 700P is finally released, I will get a Treo 650. The only reason why I wouldn't get the Treo 650 right now is my Treo 600 works perfectly and I'm not the type of person to buy the latest thing just for the sake of it when my older item works perfectly.
I use my Treo 600 for phone calls (obviously), listening to MP3s, doing the regular PDA stuff (agenda/calendar, etc.), playing games while I'm standing in line or waiting for something, reading e-mails (rarely send because I don't really like using the keyboard), short browsing of the web, taking pictures to show people, checking stock quotes, instant messaging, and now I use it in my Mandarin class to look up words using PlecoDict.
By carrying my Treo 600 around with me, I don't have to have a separate PDA, phone, MP3 player, pocket game system, and camera. Of course my Treo 600 doesn't replace my MP3 player or my digital camera but it does allow me to listen to MP3's without having to remember to bring my MP3 player with me and it also allows me to take a picture when I don't normally have a camera with me.
The only negative thing about my Treo 600 is the resolution (160x160). Reading the majority of Chinese characters on the regular PlecoDict screen is almost impossible. Without PlecoDict's magnifier feature, I wouldn't even have bought a Mandarin-English dictionary for my Treo 600.
The Treo 650's higher resolution (320x320) would allow me to see the characters in the normal PlecoDict screen instead of having to use the magnifier feature for all but the simplest of Chinese charcters.