The 'out of the box' Proforma Sales Invoice (PI) is very different to the Sales Order. The fields available don't include the same fields as the sales order, so there's a number of gaps. For example, on a S/O you have the unit of measure field, but not on a PI, so you can order a quantity, but there's no identification of 'what' (i.e. 20 Each, 20 Cartons, 20 Pallets?). This alone makes the PI fairly useless. The Ship To fields are missing entirely (why?, usually the parties want to know exactly where the shipping is going), and there's no item number field (really... ?). Agent fields are missing (so how is it shipping if its' the sellers responsibility to ship the goods...), and where is the Product Code? (sometimes several products can have similar descriptions but be unique, so the code is important).
What would be good would be to include all fields available in the Sales Order report in the PI report, as the PI 'usually' (yes there will be country variations, but generally) follows the S/O.
I'm somewhat staggered as to why fields like homepage have been included but important item fields are missing.