Make sure your system has broad support
An AMS vendor pointed out to me recently the danger of buying a new AMS (or any enterprise software, for that matter) based on the passion of one person. As he put it, "I have seen this more than a handful of times, but when that one person drives a system and they leave, it can fall apart quickly."
This raises a larger point that I always state to my clients: "When this project is done, I get to leave, but you're going to have to keep using this system." In other words, in order to be successful long-term, you're going to need buy-in from a majority, if not all, of your users.
So whether it's an AMS or any other software that has to be used by a number of staff, do everything you can to get as much consensus and buy-in as possible. The fewer number of staff that have buy-in, as staff turns over, the likelier you are to reach a point where no one likes the software (because they don't really know it).