There's a few threads on HoFo about this...
I still use my VZ 755p for business work. If you're really into the Palm OS, you'll miss:
-System integration of Contacts.
-Tasks and the reminder alarm.
-Notification for upcoming birthdays.
-Voice dialing (my 755p has VoiceSignal, now owned by Nuance).
-MMS (I'll admit that the built-in text messaging for the Treo is hard to beat, period).
-The ability to schedule your data connection - I can't turn syncs off and on like I can with my Palm (my dad's a night owl and sends mail at 1-3 a.m. and the tone wakes me up if I forget to leave the iPhone out the room when I hit the sack); cycling the data connection really cuts down on battery use, too.
-The Treo's Calc app really makes the iPhone Calculator look only slightly better than an abacus.
-I miss some of the alternatives and enhancements available for system Treo apps, like VolumeCare.
-I miss Copy/Paste sometimes.
-The keyboards are a wash - a virtual keyboard or tiny chicklets? I'm 6'7" 230 - all phone keyboards are kind of small to me!
I'm slowly weaning myself from the Treo. Palm Desktop is outdated and crashes my Mac; the Palm OS doesn't get much attention anymore - Palm doesn't own the OS anymore and updates are far and few between, for example, BT didn't even work well or properly until the 1.08 ROM update came out a few months ago. The Java VM isn't supported or publicly available anymore.
The 2.1 FW update for the iPhone seemed to help, and 3G or WiFi is available most of the places I work. iCal isn't perfect, and I'm looking to move from MobileMe to www.01.com or some other solution for scheduling (01.com has both Treo and iPhone support for their hosted Exchange solution to go with desktop and web access at about the same cost of MM for a few users). If the 2.1 update works, I'm thinking of moving to a VZ phone and ditching the 755p. Mobile Safari just makes Blazer look like a kid put together Blazer; I've noticed that the Blazer web portal has not been updated since forever and I'd bet it will get abandoned when (if) the new Palm OS comes out.
I'm pleased with the iPhone so far, and I'm using the PDA less and less as time goes on, and I've had the iPhone for 6 weeks. I still use the Treo Phone a lot, but a older solid phone will work for what I'm moving toward with VZ.
