I'm happy they're replacing Andrew Jackson with Harriet Tubman on the front of the $20 bill.
Tubman was a true freedom fighter, liberator, and warrior in an American tradition we can all aspire to. But why, oh why, is Jackson being kept on the bill at all? In the kind of ridiculous "compromise" that can only sound logical in Washington, Jackson is being kept on the back of the bill, which means we have a freedom-fighter and liberator on the front, and a slaver and genocidal war criminal on the back. Idiocy.
I have never been thrilled with Alexander Hamilton on the $10 bill. He was never President, and no one can tell you what he did without running to Wikipedia or attending a Broadway play. That said, he was important to the history of this country for many reasons, if for no other reason than his actions with dogs (specifically a white foxing terrier which we would now call a Jack Russell) during the Revolutionary War. That story is told here.