this works fine for a specific user login:
global $user_login;
get_currentuserinfo();
if ($user_login !== "admin") { // change admin to the username that gets the updates
add_action( 'init', create_function( '$a', "remove_action( 'init', 'wp_version_check' );" ), 2 );
add_filter( 'pre_option_update_core', create_function( '$a', "return null;" ) );
}
and this for a specific user id:
global $user_ID;
get_currentuserinfo();
if ($user_ID !== 1) { // change 1 to the id number that gets the updates
add_action( 'init', create_function( '$a', "remove_action( 'init', 'wp_version_check' );" ), 2 );
add_filter( 'pre_option_update_core', create_function( '$a', "return null;" ) );
}