Note: in this discussion the nopCommerce version is 1.90 and it addresses only the product category page, not the product details page. In 1.90 the old Manager classes were re-named to Service classes, but beside such naming change, most of the inside logics remain intact (as far as this topic is concerned).
nopCommerce by default uses the UrlRewriting.NET solution and it actually works wonderfully. The only thing that I don