Whilst using Xcode 4.0 and trying to debug and see what value is held in what variable - or see what objects are in an array etc, I always seem to get \"Summary Unavailable
You're not going wrong, Xcode 4 is. This problem is pretty common, unfortunately. Report it at http://bugreport.apple.com/ and hope for the best.
In the meantime you can inspect variables using the console, which appears at the bottom of Xcode 4's window during debugging. If you have an object "myObj", you can inspect it in the console by typing "po myObj". It's a lot less convenient but it's better than not getting the information at all.