Despite its brevity, the Return to Ostagar quest is well worth having since Cailan's weapons and armor are very useful and powerful. It's also very good for fans that appreciate having closure, like finding out what happened to Cailan's body. Also, this quest seems best geared toward melee characters, since there was not any loot that suited mages, even in the remains of the area where the Circle of Magi camped out.
When all taken together, Return to Ostagar provides an excellent reason to play load up Dragon Age again, if only for a little while, or perhaps start a new character. If nothing else, it helps prepare for the full expansion that will release in March.