The Clingo Mount came in and I can gladly say that I highly recommend it. I tested it out on my Incredible with the hard case. I barely press it on and the phone sticks and STAYS. I shook it a decent bit to simulate driving over bumps and it held strong. To remove the phone it peels off somewhat easily and leaves ZERO residue. They claim that it sticks to any phone and I believe it.
I bought the arm mount so I can not speak to the air vent clip. However, I would guess that the heat from the vents would not be enough to harm your phone.
Please let me know if anyone has any questions. I can confidently say this is a great mount and solution to mounting the Incredible with or without a case (or any other phone for that matter).