I've been lately using my new Nokia E61 very extensively, even replacing the zaurus as more convenient for many occasions.
Great connectivity: gsm, 3G, wifi, bluetooth
Integrated useful apps: VoIP, email (pop & imap)
Interesting 3rd party apps: ssh client (v2 with dsa private key), vnc viewer (not tested)
Can be programmed: python shell, free c++ environment
Great usability: qwerty keyboard with back lit sensor, big screen
Smaller that zaurus
Accepts mini-sd card
It's a phone!
It's not a zaurus
Wifi range could be better
Connectivity configuration menus could be greatly improved
No touchscreen? (I don't think that's a con per-se, but ...)
It's like having a lightweight zaurus with all ever-needed connectivity options. I'm planning a trip for 4 days, and I'm taking the E61 instead of the Z !!
note: I don't have any relationship with nokia, nor any other manufacturer. But maybe some developers may jump to the E61, and port OZ