Nice little module to have the price changed when the user adds quantity.
Tested in 1.7.6.7 and working.
The only thing missing is a more flexible hook to put the "You save XXX €!" message in the product page, it goes after the div "product-prices", so it is very dependant on the template you are using. It is not possible to change parent div, I tryed modifying the javascript, putting it after "product-price" or "product-discount" but it doesn't work (because those 2 divs are inside "product-prices" and there is some ajax rewriting the content, so the message disappears, it stays only if it is outside "product-prices").