From what I see, the problems are with the northeast. I sent a brake booster to a buyer in New Jersey on December 8th. The last tracking entry was St. Louis on the 16th. I fear that my package is now in either purgatory or the Bermuda Triangle. But I have still, overall, had the best luck with the USPS.
Update: After spending a week in St. Louis (Dec 16-23), my package is finally on the move.
"We live in a time when intelligent people are being silenced so that stupid people won't be offended".
