One think to be aware of is that the readme file does not appear to list the file directory structure correctly. Version 1.1.1 shows:
includes/modules/YOUR_TEMPLATE/attributes.php
includes/extra_cart_functions/absolute_products_with_attributes.php
includes/templates/YOUR_TEMPLATE/tpl_modules_attributes.php
includes/templates/YOUR_TEMPLATE/tpl_product_info_display.php
includes/templates/template_default/buttons/english/attribute_out_of_stock.php
includes/languages/english/extra_definitions/absolute_attribute_grid.php
...while the structure (right out of the zipfile) is
includes/modules/YOUR_TEMPLATE/attributes.php
includes/extra_cart_actions/absolute_products_with_attributes.php
includes/templates/YOUR_TEMPLATE/templates/tpl_modules_attributes.php
includes/templates/YOUR_TEMPLATE/templates/tpl_product_info_display.php
includes/templates/template_default/buttons/english/attribute_out_of_stock.gif
includes/templates/template_default/buttons/english/_notes/dwsync.xml
includes/languages/english/extra_definitions/absolute_attribute_grid.php