This question is maybe more about Xcode than about the Fortran compiler.
I've just upgraded to Leopard and have both Xcode 3 and 2.5 installed (and Intel Fortran 10.1.012).
Running my fairly simple projects in Xcode 2.5 works as it did under OS X 10.4 and Xcode 2.5. Running the same project in Xcode 3, I see no output window but the code gets executed.
I am working in debug mode (not release mode) as I don't really plan to build a application but only use the Xcode as an IDE. When I select Build&Run in Xcode 2.5 it builds and runs my code, opening a Run Log window to show the output.
In Xcode 3.0, building works fine and Xcode simply says 'Debugging of "xxx" ended normally'. But it does not show me any output (which is essential for 'real debugging').