is wormy firewood any good?

I burn wormy wood all the time. The borers will consume some of the wood so there will be a little less energy but most of the wood is left behind in their tunnels as worm dust. Unless the wood is so bad that it is falling apart and making too much of a mess, burn it.
Just be mindful about moving the wood to a new location and the possibility of spreading the borers if you are in an area where the borers may be emerald ash borers or other quarantined pests. From what the Department of Agriculture has told me, most borers in madrone in the places where madrone grows are harmless.