The packing slip 'feature' is a tease that makes users more mad than if there were no Packing Slip, because what is does is pathetic.  There should be the ability to customize packing slips like one can for invoices.   And creating/editing a packing slip should be an easy part of the invoice workflow, not the totally separate hunt through the Sales interface it is now.  
I just migrated from another small business accounting system that also ignored packing slips...why is this such a blind spot for accoutning SaaS businesses?   B2B companies that sell products cannot get paid without successful receiving against PO line items at customer docks.  The way this happens is via packing slips, not invoices!   Come on Intuit, you've been doing accounting software for decades, why is this feature implemented as a bug, instead of in a way that is actually useful to users?