If you're using the AC on a hot day it could be annoying. Using the heat on a cold day does the same and can also heat up your phone, depending how hot you set your heat to.
Each phone that needs to be mounted needs to have a magnet unit. If you don't use the adhesive to attach it to the phone then you can transfer the magnet between phones but that could be annoying. On the other hand, you can get more magnets and it's pretty cheap.
The grip has a sturdy hinge behind it that allows it to spin 360 degrees and tilt for a better viewing angle. The hinge has a nut that screws in to hold it in place once you have it where you want it.
The gripper is spring powered meaning it can stretch to fit a large variety of phone sizes, whether it's an iPhone or Galaxy Note. The spring is very powerful and holds your phone in place so it won't fall out.