gistfile1.js

// grab new items html
var newItems = "<%= j render(partial: 'endless_append', locals: { items: @feed_items }) %>";

// fetch the scroll position
// used to set the window location back after below hack
var scroll_position = $(window).scrollTop();

// append new items to isotope, as usual
$("#feed_list").append( newItems );

// remove all isotope functionality
// isotope is not otherwise detecting the existance of
// the newely appended elements regardless of approach
$("#feed_list").isotope("destroy");

// reloads isotope layout for entire page
// after layout callback returns the window position
// to the position before append was fired
reloadIsotopeScroll(scroll_position);

// reset pagination
<% if @feed_items.next_page %>
  $('#paginateFeed .pagination').replaceWith('<%= j will_paginate(@feed_items) %>');
<% else %>
  $('#paginateFeed .pagination').remove();
<% end %>