Hi All,
I just wanted to throw in two more cents about learning Xcode/Objective-C. The book by Aaron Hillegass is a phenomenal resource, and if you're intensely serious about learning fast, I would highly recommend attending one of his bootcamps at the "Big Nerd Ranch". I went through the 7 day course on Cocoa/Objective-C in December of 2007, and while it was incredibly difficult and insanely intense (sometimes you might find yourself working some 12-15 hours in a day, and Aaron is nothing short of superb about giving up ALL of his personal time for the students during these boot camps), the course was truly amazing. Several students there were folks that had taken the course before, but wanted to get the information at a deeper level, now that they'd gone off and gotten some more experience. I hope to do the same, as well as take some other courses offered there.
It's not cheap... but it's awesome. Aaron is not only incredibly knowledgeable with tons of experience, but he is also an excellent teacher... and that's what is so hard to find, really.
The next best thing is his book, the 3rd version just came out this past spring (2008).
Disclaimer: I am in no way associated with big nerd ranch or Aaron Hillegass... I'm just an extremely satisfied customer.
Best of luck to us all, diving into iPhone development!
Cheers,
Jon