I have recently been on an xcode course and we used version 3, I found that compared to Delphi and Visual Studio, xcode was behind the times by quite some way. To do interface design you had to use interface designer which is a separate application, so you have to keep remembering to save the interface. Also unlike Delphi there is no background complication so errors in code are not reported until you manually compile the application. The code completion is weak and no way as good as Delphi.
However, while on the course xcode 4 was release and we got to have a quick look, Apple has made a massive leap forward with the IDE and now the interface builder is part of xcode, also the compiler is new, this means background compilation is possible so errors are reported instantly and the code completion works much better.
I am looking forward to moving onto xcode 4 when I get a moment, it looks much better and now is up to date with Delphi and Visual Studio.