The biggest problem for me as a buyer is that I want to know when my parts will show up, it let's me plan on what i should work on when I get home from work. The USPS tracking number system is lacking, in that I have never actually seen my shipment in progress...I would gladly pay an extra couple of bucks to know where it is and when it will arrive, also, if there is a lost item UPS,FedEx seems to have better support programs.
Just my 2 cents...
Best of luck on your new endeavor,
Wade