Optional Install
Xcode was available through optional install on my Leopard disk. I did not see it as a custom option when installing Leopard itself ( I may have breezed by it by accident due to excitement ). However
, insert the CD and browse the "Optional Installs" folder and you'll see it.
Cocoa/Obj-c in my opinion is the way to go. I got myself a MacBook Pro back in March and started programming Cocoa a couple months later. I'm addicted, there is just so much you can do with it.
I love Xcode 3.0's Code Folding ( something I discovered tonight ); Enjoy;