Maybe it's because I'm relatively new to OS X but I find Visual Studio and its single-window interface vastly more efficient and usable than Xcode+IB and it's plethora of open windows.
Have you tried the "All-in-one" layout in Xcode? (Look in the "General" preferences section.) I find it a lot more usable than the default lots-of-windows setting, especially if you have more than one project open.
