oF is pretty much the same across the various platforms, give or take a library here and there. You can see a list of libraries included here http://openframeworks.cc/about/. C++ compilers are also slightly different between each of the platforms, as well as the way each IDE is setup with references to oF. A good overview can be found here http://openframeworks.cc/tutorials/introduction/000_introduction.html
I think the main differences between PC and Mac is really dependent on your hardware. For example with OpenGL on a Mac you won't be able to use core profile > 410 due to Apple not providing updated drivers to support the graphics hardware. This would also be true where your hardware is different: multi-channel sound playback, video capabilities and other hardware peripherals.
What sort of troubles were you experiencing when building oF on Windows? Did you use the download from here http://openframeworks.cc/download/ and follow the instructions here http://openframeworks.cc/setup/vs/? Were you using Visual Studio 2012?
