How good is cross-compiling?

I'm using GNU/Linux, and i586-mingw32msvc-gcc-3.4.5, to compile for windows. Now, I wonder :


Is the C program I compile with mingw a real windows executable? Will it run the same as one compiled on say... Turbo C? Is there a difference in speeds of compiled programs, using mingw, and any other windows C compiler?

How good is cross-compiling?
mingw compiles to native executables, so it's a "real" windows executable. Mingw is probably more optimized at this point than Turbo C. The fastest is probably Intel's C/C++ compiler, but not by much.