When adjusting the arm, you'll hear clicks as it rotates into place.  The arm is very secure and will prevent your Visor from swinging wildly around.  I noticed that while driving, the handheld moved very little (except, of course, on those Texas potholes ).

I think that usability of any mount is going to depend greatly on your vehicle.  My Toyota Celica has a curved dash, and once I had a suction cup come loose.  This caused the mount to turn and slide over.  The other suction cups held so my precious Prism wasn't damaged, but I think a built-in flip cover would help prevent any accidental disconnects.

This particular model was designed to be used by almost any handheld.  I hope that Arkon Resources eventually makes a Visor version that has the grips on the left and right sides with the Visor's Springboard slot exposed.  That way oversize GPS modules could be secured.

In my picture you may notice that I'm using a Visor Prism .  Prism owners may have trouble using any car mount because of the handheld's poor viewing capability in direct sunlight.  It was passable for me, but those fortunate enough to be driving a convertible may have problems.

That is not to say that this car mount isn't effective.  I think that traveling professionals would like to have essentially hands-free Visor use, but don't let me catch you driving while reading your AvantGo channels!  I also feel that as voice recognition starts taking off in handhelds, you'll want to have an accessory like this so you can always have your Visor ready to go.

For those looking for a more secure mount than the windshield model, Arkon also has available a Multi-Angle mount kit (model CM228) that I also think would be perfect for those on the golfcourse who are using IntelliGolf.  The multi-angle kit attaches to your car's dashboard using three (included) Phillips screws or an adhesive pad.  The gripping mechanism that the Visor attaches to is the same.