Well, milk that gets old in the refrigerator is not worth keeping. Surprisingly, there was very little smell, good or bad. The liquid portion tasted unfit for consumption (so I did not). It was not quite milk-colored, and I can confirm the "metallic" taste. The top layer, on the other hand, was literally cheese. There were at least two kinds, one of them cream cheese, the other was familiar (kind of rubbery) but I couldn't identify what it resembled. Regardless, after the third or fourth nibble I decided that they were they worst cheese I had ever had, possibly including "cheese product". Certainly not worth the effort of spooning it out.
Anyway, I did that on an empty stomach, then had a couple eggs. It's been four hours, no symptoms. I have thrown the milk away. At some point I'll make cheese properly.