I just made the transition from my Palm 650 to the iPhone last night. No problems. I already had iTunes loaded on both my laptops and hooked up the iPhone to my work laptop and when it set up to sync, I told it to sync all my contacts and calendar stuff from Outlook to the iPhone. It took about 10 minutes to complete.
When complete, I checked and all my contacts and calendar entries were there. I then hooked the iPhone to my home laptop where all my music and photos are stored and again, through iTunes, it sync'd all my music, then photos. I since deleted all my photos, as they didn't come across onto the iPhone as I hoped. I sync'd it to the one folder on my pc where all the photos are, and although I have them nicely organized within that folder, by many other folders, all the photos all just came to the iPhone under one folder. No good. I'll have to figure out how to keep them organized.
Hope this helps.