Bumpdate to crow SUCCESS!!! (thanks to tips from y’all).
The stock was sitting in the fridge until this afternoon when I got it out to use it for its intended purpose (the vat of veggie-beef soup that’s simmering on the stove right now). I pried off that orange disc of fat (orange because of the tomato paste - think I might use a bit less of that next time), threw that out, fished out a quarter cup of stock to taste, and set the rest to simmering after adding in the beef cubes and THEIR water (slightly defatted - as I’d trimmed it before boiling separately, there wasn’t that cohesive disc like on the big pot).
I zapped the stock for 30 seconds, and added a few grinds of salt (too much as it turned out) and tasted - and it was actually good! Not 'famous the world around" good, but pretty darned flavorful.
So all in all: it was only a little more effort, though the expense was certainly higher than usual. I had to rejigger my timing slightly by doing the trimming/defatting of the actual meat at the beginning vs. while the bones were roasting.
Would I bother again? Only if I needed something with very significant flavor on its own, where Swanson’s wouldn’t do. If I needed it for, say, a clear-lquids diet, maybe - but it’s a lot easier (and requires less preplanning) to just pop down to the nearby pho shop and get a couple quarts of their broth which is delightfully fragrant and has just the right mix of sweet and savory spices (anise? allspice? something else?).
On the subject of chicken stock: We’ll save several carcasses in the freezer and boil up a vat of stock made from all that and it’s decent. Not “drink alone” decent but good enough that I’ll enjoy it with some carrots / celery thrown in and ladled over noodles, and good enough for other recipes.
The absolute best stock I make, hands down, is what comes from the Thanksgiving turkey: we brine that, and the brine has salt (of course!), sugar, apple juice, allspice, cloves, pepper, ginger, and bay leaves. So when making chicken soup at other times, I’ll usually add allspice and cloves in addition to the more traditional pepper and bay (must remember to add ginger next time…).