I just updated my Treo 700W to to the Samsung SCH-i760 and in the process noticed something missing. Specifically, Pocket MSN (Messenger, Hotmail, etc).
Did some digging, and found out that these applications are now available from Windows Live as links from your mobile phone. You can browse to these services by directing your phone's browser to http://mobile.live.com.
You can get more information on your desktop browser. Check out:
For more information, check out the Windows Live for Mobile home page.