Nullification is rare and unfortunately that line of defense largely failed during the drug war. But I think that's largely because the government was able to successfully make it a racial issue. It's not always easy to take advantage of deep social divisions for all kinds of policies, and that's why dictators don't like juries.
Kind of like guns. How useful are they against tyranny really? Useful enough that tyrants try to take them away, and that's all I need to know.