Both Palm & Blackberry offer "Push" email applications. I find the Palm more user friendly in the real estate world, advanced users though will find both equally good for their purposes. Lack of built in Wifi for the Palm is really the major tech item missing. One item to be aware of is to be aware of is the vuneralbilities of wifi and bluetooth access and the info stored on your handheld.
I have not been happy with the PalmTreo. Freeze frames - locked up phone, shutting down for no apparent reason...the list goes on an on. I have been looking at the i-phone and the main reason I like it is because I can actually read the screen.