Food hygiene experts needed

On a whim (vaguely inspired by a thread on boingboing) I made butter today out of some cream that had gone off. I've tasted it and it tastes fine, but I'm still wondering if there could be any kind of health hazard, because the cream really was rather old. The cream was about three weeks past its use-by date; it was organic cream without stabilisers or other additives, unopened and refrigerated all the time. It had separated into heavy sour cream and, well, a thinner, less fatty component that wasn't quite whey yet. I beat the whole contents of the packet until it turned into butter, poured off the whey, and washed the butter in a sieve.

So... think it's safe to eat? As I said, it *tasted* fine - but I've only tried a tiny little dab, so far.