The best thing about stacks is that it has very clear documentation, which makes training new employees easy! Also I like how you can easily add more fields to your forms without having too much of an impact in terms or design/functionality (it's still pretty simple).
Nothing really - just try out their free trial if they have one available for testing purposes before purchasing anything from them as well since there are other options such at SurveyMonkey etc., but stack seems better than those two by far when comparing ease-of use! We're using this software mainly so we don't need our clients filling up surveys themselves anymore instead letting us do all work related with survey creation & distribution through StackData!!