After my Samsung Tab 2 7.0 got upgraded to 4.1.1 the main buttons changed place. Back used to be to the far left, now it's the second to the right, for example. This is amazingly annoying.
When it was new I did find some way to change these things, so I could get rid of the annoying Screenshot button that was installed by default. But after the upgrade, the possibility to configure this seems to have disappeared.