I use pirateship and appreciate the savings and simplicity.
A counterpoint: I have seen far more denials of insurance claims here and elsewhere for all the shipping companies than I would think was reasonable. If a claim is made for a lost/damaged $1,500 item, I would certainly expect a denial and the need to fight it. I have figured in my head that I would have better legal footing if I walked into the retailer (USPS, UPS, etc) and paid for shipping and insurance directly to them. Reason being, they offered a product/service which I then paid for. If they denied an insurance claim because of some fine print on page 68 of their service contract, I could reasonably ask that they show where I signed that contract or where on the store video while I was purchasing the service that the contract was shown to me. I have purchased insurance many times through the various shippers, and have never been shown or told anything about how they exclude certain claims, other than the normal questions of shipping flammable, explosive, lithium, etc.
When using pirateship, even when adding insurance, the shipper could just point back to pirateship and say it's their fault that the terms of insurance weren't properly explained/followed.