Ptaaaaang!
It seems like getting them up to terminal velocity helps make the landing more survivable for them!
http://www.todayifoundout.com/index.php/2010/11/domestic-cats-can-fall-from-any-height-with-a-remarkable-survival-rate/
So you need to make sure your cat-a-pults are up to the job.
The biggest problem I can foresee is actually the injury rate to the poor 'handlers' that have to load them into the cat-a-pults! Those poor people will end up suffering quite a blood loss on the average day!
