Don't use USPS for heavy packages. Use FedEx like USPS does.
My experience with USPS has been great. Less than 1% of my packages go missing, and the broads at the front desk are really nice. The shipping prices did jump on Ebay, but I mostly use flat rate envelopes, and medial mail, so it doesn't affect me that much. USPS raises prices every year, so I ain't surprised. Whateva.