Great thread! Thanks for all the great replies. I was just re-reading
all the comments and thought I'd make the following comments:

Sadly, it is a new-to-me saw, so there's no warranty.

There is no vibration when the saw is running with any blade. I am
using the arbor nut and washer only, I'm not using a blade stiffener.

The blade is sharp and spankin' clean.

Trouble with re-adjusting the blade alignment to average out the error,
then cuts using any jig that relies on just one miter slot will suffer
from burning or chiping, right?

Would there be any way for me to re-machine the wayward miter slot, or
would I have to take the top to a machine-shop? If I have to take it
to a shop, what would I be asking for (so I don't sound too stupid)?
What sort of cost would I be looking at?