I'm starting to learn development for the mac (then I'll learn iOS development). I just buy an iOS developer program, and I see there are 2 IDEs available for download: Xcode 3.x and Xcode 4 (GM Status). So I don't know where to start. Site's says that Xcode 4 its now "integrated" so there is one app instead of 3, and that it's better for small screen because tabs and other features (I'm using a 13" macbook). But looking for books I see books only for 3.X. I'm a C# & .NET programmer, I know that the fundamental is the language and the framework (Cocoa) but I've been told that getting proficient with Mac Dev is getting proficient with Xcode.
I think that if I start with Xcode 4, then I'll learn on the "next" IDE and since I have no hurry I can wait until apps made with Xcode 4 are deployable (on the app store). But, maybe I'm wrong and I should start with Xcode 3 and the largest set of books and references available.