Down here on the 28th Parallel they are great if you want the top of your head broiled or wet. During a summer day it's too hot and humid even if it's cloudy and not raining, and at night during the summer it's too humid to have the car opened. When the conditions are favorable in the winter to open it the noise makes all that money you put into the stereo wasted - and you have to wear a hat to keep the glare off the back of your glasses.
That having been said, there has been one on every car or van I've owned for the last 16 years (except for the convertible and the Jeep Commando, which I take the top off of whenever I can)- six of 'em, from Kias to Mercedes, and I've never had one fail or leak. The have all worked just fine - I just don't like 'em, but then I'm bald for all intents and purposes.