Back Touch Button does not respond good. how is your phone?

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http://forum.xda-developers.com – hi, There are 3 Touch Buttons at the Bottom of Xperia S. Back, Home, Menu These 3 Touch Buttons does not respond very frequently. Back Touch Button is the worst. And This annoying me very much.. How is your Xperia S? Do you have any tips? (HowTos)