Like others have noted, the thing is perfect for the first few months and then the foam bottom gets less "sticky" over time. I don't use any armor all or anything but windex on the dash. The foam just loses its ability to grip. What helps is scratching the foam up to restore the grip. But...you can only do that so often before you are left with no more foam. 

Question: How helpfull could be this unit?
Answer: the thing is perfect for the first few months and then the foam bottom gets less