"If the order contains both shipping items and non-shipping items, the shipping cost is computed on the total order amount rather than just the total of the shipping items." - I work with a number of open source ecommerce projects and none of the table based shipping modules would do this, it would be custom.....it should be determining the shipping based on the subtotal of the order, if rates are based on total order amount..custom code would be required to parse the shopping cart for attributes set for "free shipping" or "no shipping required" products in the order.


"If the order contains discounted items, shipping cost is computed on the total non-discounted prices." - that definitely sounds like a bug, it should be looking at the sub-total - but I would need to see it in action

you might want to go read the description onhttp://www.concrete5.org/marketplace/addons/free-shipping-by-produc... to see if it comes closer.

The other way I would deal with this, in Zen Cart and using table rates, is to go with determining shipping by weight and making sure "non shipping items (virtual?)" have a zero weight, then only those items with weight are used to determine where in the table they fall for a shipping cost.