Hello Aaron,
The only fully implemented use of finstack for me so far was strictly for the tenant feature (running on top of Niagara Server). This worked out very well. I have been in contact with Ricky on some suggestion for improvements, but it is much nicer than the CSI3 tenant billing (tenant eye) we had been using. Setting up tenant eye took about a week, finstack took about 2 days once I knew what I was doing.
The other licenses are for upcoming projects which I have not started yet, but I am using fin 4.0 for all of them. I am sure I am a couple of revs. Behind by now, but I downloaded the newest version about a month ago. I will probably, at some point in the not so distant future, still need your help on my first real implementation.