Joe,
From a customer perspective, I would be far more likely to take my car to a shop who had a dyno in the first place. Having a dyno may attract more performance based clients. In my case, I am considering having a dyno run after you are finished to complte any fine tuning, but I would have to find someone who had a dyno and who know the TEC GT system as well. The pond is pretty dry. I would love for you to have one, I am just not sure how many hours of dyno tuning it would take for it to pay for itself, and how many customers you will have that want a dyno run. If it is two or three a year and a couple hours a pop, it may not make sense.
On the one hand, like Jake said, you don't want to advertise it and bring in the knuckle draggers, but on the other hand you may need to let people know you have that service to bring in the additional clients to justify having it.
If you get one, will you have it installed and ready for a run on Saturday???