I've heard of this but never actually seen it. Are the falls frozen over?

Nope; there's just too much running water for them to freeze, but they're frozen around the edges, the river is mostly frozen, etc.

If you look at the pics that I posted on LiveJournal, anywhere you see banks are frozen over, but the falls themselves are still running. All the area that's got coloured lights on it in this photo is running water; you can see from the photo of the American falls (http://www.furaffinity.net/view/5178296/) that the areas with the yellow and purple lights are running water, but it's all ice-covered between them and around the edges. It's hard to explain; just look for glossy water vs. rough ice/snow-covered areas; more noticeable in the other photo.