[рони]

solunski.d,
так будет проще

$(function(){
    var $ul = $('.filter_1'),
        $button = $('.filter_other1'),
        n = true;
   $ul.scroll(function () {
    if (this.scrollHeight - this.scrollTop === this.clientHeight || !this.scrollTop) {
         n = !n;$button.val( n ? 'вниз':'вверх');
    }
});

   $button.click(function () {
        $ul.stop().animate({
            scrollTop: n ? '+=100' : '-=100'
        }, 1000);
    });
});