The only other cavaet about hard shell cases is that in the past 7 trips to the US we've twice had our locks cut off our cases by Homeland security (can't remember their exact name TSA or something), and had to buy replacement locks, other people on our flights had the locks on their hard cases broken open - at least we have the option of just buying a new lock, their bags are beyond repair, and you don't get compensation.
(I've since ready that if you have books in your case they come up looking 'suspicious', so as I go mad buying books in Barns and Noble every time, its probably why my case has been checked).