I worked for UPS...I would personally NEVER recommond them. They train their workers to "build walls" which translates into taking a package and making it fit into a hole, doesn't matter if its too big or not. Then when the wall is almost build, you have to throw boxes behind it to fill any holes between the walls. Ever wonder why your boxes are crumpled or smashed? things are broke? in ups-ense "fragile" is a challege not a caution.
I too was a member of the teamsters union when I was 18. Yes, they build a wall with larger boxes (think tetris) and anything small gets thrown on top/behind the wall. I put my foot through more than a couple larger boxes too (as do many on the local sort). Truly, never ship something fragile in a small box via ups. I worked with a crazy kid named bobby who would huff 108 octane race fuel until his eyes popped out of his head - we didn't talk much...
USPS Priority and 1st class service are way different. 1st class goes through way more mechanical sorting and the package gets dropped way more often. Priority mail is actually handled by hand more often than not, meaning the package is very rarely dropped or thrown, but handled by career postal carriers who answer to a postmaster general (who takes complaints VERY seriously). I'd say the government has been losing money on the USPS for many years, thus the steady hike in postage - inflation not withstanding.
I don't know a lot about fedex, but I do know if you ship a huge volume with them they will give you as much as a 70% discount on a shipper account, especially if you threaten to use UPS.
I don't think anyone has a gripe with HKEMS, aside from paying a premium by the gram. And yes tracking is weak across the boards.
Shipping times are about to slow down dramatically for all carriers due to double or triple the volume for the holiday season. At the end of the day each facility can only handle so many boxes per hour. They bring on temporary staff, but only so much is really possible.
The only practice I would frown upon is using a flat rate envelope for ecigs - I don't think anyone does this, and it wouldn't even be a problem 95% of the time.