I went a very similar route with my set up. The main difference is the mounting system i used. I originally ordered the same part but changed to this option (
http://www.amazon.com/gp/product/B0012T ... 02_s00_i00 ). I used one of the two mounting bolts for the rear view mirror bracket. It keeps it nice and snug especially for vibration purposes.
http://www.amazon.com/gp/product/B0012T ... 02_s00_i01 this is the arm piece it extends just up past the cluster area.
The setup definitely dampens vibration very well, most of it has to do with the x-grip system of course, but the mounting has a bit to do with it.
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http://www.youtube.com/embed/Irh8stSyWAs" frameborder="0" allowfullscreen></iframe>
And also as you can tell, there is very little chance that even while going over bumps or at high speeds your Phone or GPS will slip out, which was a concern to me considering mine is usually a $500 phone. This thing holds it super super well.
It has been amazing so far, using google maps and choosing to avoid highways works great, and with this mounting system it brings the device into perfect view of the cluster area without getting in the way of the handlebar area or the view.