They are useless at finding a connection like GTO-CGK. Like most US travel sites their value is limited to what is in the US and the major overseas destinations.
For example I can beat any price on most 3-5* hotels using local hotel brokers. Unfortunately these brokers don't operate on the web. Most savvy travelers can also negotiate prices directly with the hotel reservations department to get the best rates.
Anyone who comes to Indonesia frequently should be mindful of this!