I switched to the 755p recently and searched far and wide for an MSN Messenger application that would not charge me and SMS fee. It's features are outstanding. This program, QuickIM, works just like the desktop version of MSN Messenger.
It was easy to setup on my Treo 755 from Verizon. I like that QuickIM wil run in the background while I am doing other things. I recommend it! Its the first program on my list.
You can download a free trial from
www.QuickIM.com