To be honest, I've been spoiled - I am too used to Delphi's IDE (which is pretty good, but not stellar) and its debugging (which is absolutely incredible). XCode offers similar debugging, but not quite as user-friendly as Delphi/C++ Builder.
As IDEs go, a great many offer some good tools but I find I'm just as happy writing code in a syntax-highlighting editor. But when it comes to debugging at runtime, you can't beat a good IDE in my opinion. At work, with 2.5 million LOC spread across about 80 or so libraries, debugging would be an absolute nightmare if all I had to rely on was GDB.