I tried installing this mod on my new 1.5.7 install on Friday evening (have it on my old 1.3.7h working fine for years) with the Westnminster-new template and it didn't like it at all. Followed all the steps in order, did the tax changes, etc. It didn't activate in the admin area, and then when I went to the storefront, no products were showing. Went through all the files again to make sure I hadn't missed one... nope, all there, So i uninstalled it and will hope that one day it actually becomes a built in feature as it is a very handy tool to have when clients want to add to their order.