Good question. The one thing that I always attempt to glean from the sales reps that I deal with is how are other large end-users are using the systems that they sell. Beyond the basics - what type of enterprise-level reports do they use to ensure that the system is working effectively, how are they notified when troubles occur, what type of integrations do they have, what is their retention time, what type of storage do they use (NAS, SAN etc), how is the video displayed, do they utilize rule based pop-up video, what bit rate and frame rate do they use? etc.
Many times as an end-user you are on an island as you are only familiar with your current system and others that you have dealt with in the past. Going to the industry shows like ASIS as well as this website help - but diving in deeper into the full capabilities of your product would be of interested to at least this end-user.