Grant Rettke points to a discussion in the comments from a Sacha Chua post. It turns out that when you're in multiple cursors you can narrow the view to just those lines having a cursor. That's something I didn't know.
All you need do is turn on
hide-unmatched-lines-mode. You can do that by typing 【Ctrl+'】. This is nice because it eliminates a lot of clutter and allows you to concentrate on the text you're changing. Where is really shines, though, is with a large buffer where you normally wouldn't be able to see all the cursors.
hide-unmatched-lines-mode will provide some context—2 lines above and below each cursor, by default—but, of course, you can configure that. This is another great enhancement to one of my favorite packages. Another gift from Magnar Sveen.