After having "converted" SFML into a fully portable library (ios/android) myself, i remember a few bumps on the road:
sf::String ->
http://stackoverflow.com/questions/5630255/does-android-not-really-have-wchar-tAudio -> needs a very specific backend to work
ios EAGL -> the default framebuffer is not the window, but a off-screen fbo now.
OpenGL ES -> went with a renderer base class and specializations for each OpenGL version
Texture::copyToImage() -> not possible anymore, breaks some code
sf::Shader -> would probably need refactoring (GLSL ES and GLSL are not equal)
Assets -> Stored in a zip file, instead of loose files in android. some formats will be compressed unless you do some tricks.
I don't remember the rest of issues right now, but i ll update later if i do. I think it will be a little harder than expected to have sfml fully working in android, in particular.