^^ No, I'm not - at least not yet. My garage is attached to my house, so it stays relatively warm. My curtain installation required about a 15" gap at the top, so I wasn't too worried about 'sealing off' the 3rd bay. In my case, the main purpose of the curtain is to stop the kids from entering the 3rd bay where the Camaro and Land Rover Air Portable are stored. It will also stop the occasional runaway trike, basketball, frisbee, etc. Another benefit is when you get a nice warm humid day outside but the garage and cars inside are still cool, the curtain should help minimize condensation on the cars.
In the future, I am considering adding a filler piece between the curtain and the ceiling and running a dehumidifier. I'm not sure if I will ever do it, though. I've been storing classic cars in the garage for 12 years, and I haven't had any issues due to temperature or humidity (other than a little condensation on rare occasions).