If you are as busy as I am, this is the module for you.
I had to constantly admin my related products. If one item was discontinued, I had to find every product associated with it, and replace it. I also had to determine what items are best associated with the display product.
Holy cow. For the price of this module, you could save hours and hours of that stuff. You just turn the module on, and tell it how many related items to display! It even gets "smarter" with every order placed.
If you have more than 30 products, I would jump on this module. Install. turn it on. Forget it. Never admin your related-products again.