The message here, is to get references. Call those references. I like to throw the vendors for a bit of a loop. I ask them to provide a BAD reference. Let's face it, not every single installation is perfect 100% of the time. I can always provide you a list of happy customers, that's easy. But the reference I really want to talk to, is the one that had problems with her implementation, and then assess how well those problems were remediated.