As a buyer who buys from the US a lot I don't think there's much hassle. I have paid using PayPal, engergyflow.com, cash-in-the-post and others. Most of my shipping has been by USPS and out of 50+ packages none have been late, lost or damanged, a few others were by FedEx and UPS and were fine. If you need to under-declare the value then I don't think it matters who use you to ship packages as for FedEx and UPS I don't think you can use different values for insurance+customs. USPS is always at least 1/2 the price of the others, and for heavy items they are way cheaper.

On ebay, I have only been refused permission to bid a couple of times from people who have "USA only" in the description - I find the final price is lower because they don't allow international bidders, and other people can't be bothered to ask.

Gareth