We've recently added the USPS Saver choice to the list of shipping options and are experimenting working with the post office for smaller sized orders. UPS and FedEx both recently raised their ground service rates, it especially affects smaller sized orders under 6 lbs. We know that shipping can be costly, especially on small orders so we are hoping that by offering a better option through the post office we can help everyone cut down their shipping and handling costs.
The post office does take slightly longer to process and deliver orders, it's tracking is also not as accurate as UPS or FedEx but there is a decent price difference in the services for small packages. Once you get into larger sized packages, the shipping rates become very comparable across all the services so we will continue to use UPS exclusively for the larger sized orders.