Guys if rooting the android device is an useful one or not?
It is very useful. You can flash custom ROMs (and leaked stock ROMs) and themes. You can install the awesome app Ad Free to block 95% of all ads. You can use wi-fi tethering for free. You can uninstall carrier apps that you don't use (bloatware). You can overclock/underclock your processor. You can flash custom kernels that can help battery life and increase overall performance. You can easily backup and restore your data with a custom recovery.