This release isn't done yet though: "Redo" has been added in -- when you hold the Undo button down in the app, you'll get a whole menu of different options to go to various points in what you've done so far. And the Zoom function has been tweaked and improved as well, offering a quicker response and a better resolution, even when zoomed in.
I'm a big fan of Sketches, and expecially of the app's ability to let you pull in a background from almost anywhere (from your phone's camera to the Google Maps app), and then make your own marks on it. It's more than just an art app -- I've used it as a memory jogger, and even as a way to quickly send directions out to others via email or Twitter. It's available to new users on the App Store for $4.99, or the 1.7 update is free to those who already have it.