Are you a one or two piece person??
Do you want it all (phone, PDA) in one or would you prefer the potential flexibility of two devices?
As I have been writing, I really dig my T-610 phone… It’s very powerful and can serve as a modem with the right data plan for my laptop as well as a bluetooth PDA with and without wires. My current PDA, the Palm Tungsten C will never connect to my phone unless I use IR, which will work but is slow and you actually have to have the devices lined up.
The current options for bluetooth enabled Palms are basically the Tungsten T2 or T3 or the Clie UX-50. Only the Sony has a keyboard, but the T3 has a killer screen. The Sony is $600 with a $50 rebate which is pretty expensive, though it also includes WIFI.
Thinking back to the Treo 600… I’d be able to use one device as phone and data connector (email and web) and swap the SIM card back to my T-610 for bluetooth connectivity on my laptop when needed.
I would still retaining my “other” phone keeping me a two piece (or even three piece) guy.