This is a good functionality that I foresee will benefit many customers. But I would like to add the funtionality of allowing posting of items with this settings if shipment or receipt has already been made. This could be a setting in the sales & recievables and Purchase & payables setups since there could be a difference between the flows. As it is, it works exactly like "blocked" except that it is split in two. If implemented, it would help control item visibility on a web shop too. However, if item is already shipped (and warehouse therefore empty), it should still be possible to invoice it!