I have never been able to carryon my cue cases but I recall some folks having been able to ....wish I had been able to go thru that line instead! In any event, I don't have any horror stories of my own about my checked cases but one guy who went out to APA Nationals had issues!
We flew out of Boston, to Milwaukee and then LV and although the tags on the bag that my case (and only my case...which was a tight fit) was in were wet. The bag itself appeared dry and was actually of a water resistant material so I had no issues and really never gave it a second thought.
Later, when I ran into this player from my state, from a different team and area, he told me how his bag with all his clothes and cues/shafts, etc. got TOTALLY soaked and everything was destroyed, I was shocked! He spent a good amount of time running around to vendors replacing equipment before the tournament started. Sure the airline is going to reimburse him but if you've ever had to work thru that system, it's a joke and a hassle. Some of his stuff was irreplaceable or so he claimed. I don't really know what he had so I can't say.
The main take away.....anticipate the worst, take precautions, leave the really good stuff at home unless it is a "must have" item and DOCUMENT it all before leaving. I have a picture of all my really good stuff that I provided to my insurance agent because I have it all scheduled in the event of a loss.....It's an inexpensive rider....like $60 a year for around $2k worth of coverage.