As someone else noted the only issues with the using the vents to hold the phone is that they do occasionally fall out of the vent and or cover some of the CD buttons or other radio selection options. And when I grab the phone quickly to exit the car the part that fits into the vent sometimes likes to come with it and I have to take an extra second to "slide" the phone off the magnet.
The one on the RV is the best location but my car and van didn't have what I considered an appropriate spot on the dash at an angle or distance that I liked better than the vent area.