asterisk/UPGRADE.txt

Information for Upgrading From Asterisk 1.0
===========================================

Agents:

* The default for ackcall has been changed to "no" instead of "yes" 
  because of a bug which caused the "yes" behavior to generally act like
  "no".  You may need to adjust the value if your agents behave 
  differently than you expect with respect to acknowledgement.

Dialing:

* The Caller*ID of the outbound leg is now the extension that was 
  called, rather than the Caller*ID of the inbound leg of the call.  The 
  "o" flag for Dial can be used to restore the original behavior if 
  desired.  Note that if you are looking for the originating callerid
  from the manager event, there is a new manager event "Dial" which 
  provides the source and destination channels and callerid.

IAX: 

* The naming convention for IAX channels has changed in a minor way such 
  that the call number follows a "-" rather than a "/" character.

Applications:

* The CallerPres application has been removed.  Use SetCallerPres 
  instead.  It accepts both numeric and symbolic names.

Queues:

* A queue is now considered empty not only if there are no members but if
  none of the members are available (e.g. agents not logged on).  To
  restore the original behavior, use "leavewhenempty=strict" or 
  "joinwhenempty=strict" instead of "=yes" for those options.