Are there any real benefits to using PXs and BXs in today's military? If so, what? If not, why?

Depending on what state you are in, not having to pay the sales tax can be a big benefit. Especially when buying larger $$$ items.

I'm all in favor of a CONUS only Government owned contractor operated facility slap a walmart logo on the buildings for 20 years with contractual language that their prices must match the off base prices, with the benefit of no tax.

Keep AAFES/Navy PX for OCONUS only.

I think that a major point is being missed... Military Reserve Scotch. You know it's good if it's in a plastic bottle.

Well, as a resident of Virginia who was stationed in Virginia, I can say that I miss the prices at the package store for booze. Virginia has the highest liquor tax in the country. The price for a keg was usually pretty good, too, as I recall. Not, that I need those very often...