Seriously, the Ethiopian UB is crap even when played with unrestricted leaders. The only time it makes sense is in a Pangaea culture-victory attempt with a non-creative leader, and even then, you're better off with China.
But on the topic of Stonehenge, I find it much more useful in BTS than I did in vanilla Civ 4 because it doesn't expire with Calender. I normally wouldn't delay Calender much, even with it obsoleting Stonehenge, unless you have no calender resources. Stonehenge is awesome in that it saves hammers in new cities, hammers that could be better spent towards granaries, etc, and is actually quite useful in a war to get control over conquered territory. However, I rate it as a waste of hammers if you have a creative leader or are playing as Inca (especially Expansive Inca w/unrestricted leaders)
But on the topic of Stonehenge, I find it much more useful in BTS than I did in vanilla Civ 4 because it doesn't expire with Calender. I normally wouldn't delay Calender much, even with it obsoleting Stonehenge, unless you have no calender resources. Stonehenge is awesome in that it saves hammers in new cities, hammers that could be better spent towards granaries, etc, and is actually quite useful in a war to get control over conquered territory. However, I rate it as a waste of hammers if you have a creative leader or are playing as Inca (especially Expansive Inca w/unrestricted leaders)