Also a Ruby programmer, and I'm currently on lecture 5 and assignment 2 of the Stanford course, and I'm finding it very good. I've dabbled here and there with various Obj-C tutorials, but this course takes you from knowing nothing about Obj-C, Cocoa Touch, and XCode, right into building apps. Because it is targeted at Computer Science majors who already know other languages there is no basic-level stuff like, "This is a loop", "This is what object orientation means", etc.

I don't think of myself as a visual learner and I tend to avoid screencasts in favour of reading, experimenting, and hands-on learning, but the difference between web development with Ruby and mobile development on iOS is so big that the methodical, step-by-step nature of this course is helping me.