Amnesiacv2, I've had four shipments via USPS, all my shipping notices were sent on a Friday and all but one was received on Saturday. The other one was received on Monday. I do the once a week, Thursday, shipment option so I'm "assuming" that it was actually sent to or picked up by the Post Office on Thursday and the notice gets emailed on Friday. In any case, way better than the 7 to 8 day UPS time.
YMMV depending on your proximity to a major city. I'm in the Bay area so it seems to be pretty consistent.
Good luck,
thurs