ROS 1.1.5 has been released against latest. The ROS 1.1.x series is an
unstable development branch for new feature development, so it is only
recommended that users update if they are already using the ROS 1.1.x
series.

The full changelist for ROS 1.1.5 can be found at:
http://www.ros.org/wiki/ROS/ChangeList/1.1#A1.1.5_.282010-05-12.29

 -- your friendly neighborhood ROS team