I've never gotten one myself, but every time I see a car with a "Denver Boot" on it, I think, "What a nightmare." The car owner has to go downtown during business hours, pay the fine and then go back to their immobilized vehicle, waiting for a city employee to show up and remove the boot. All because of unpaid parking tickets. In case you're wondering how the Denver came to be notoriously and permanently linked to the wheel-clamping device:
The Denver boot was invented and patented in 1953 by Frank Marugg, a musician for the Denver Symphony Orchestra. As a good friend of the Sheriff, he was asked to build a device to immobilize automobiles whose owners didn't pay their parking tickets. For decades, Denverites have simply called the device the "boot" and use the term as a verb ("to boot" a car).
Here's a heads-up. Relief is coming in October. Denver has announced it is moving to a "smart boot" system. When you see the dreaded boot on your car, you will be able to call in 24/7, even by cell phone, pay the fine by credit card and have the boot "released on the spot." Now that's progress.