As mentioned in the README, the feathersui-xml library is considered experimental. There are definitely bugs. However, I have been working on a new library that will be a much more complete implementation of an MXML-like language for Haxe. I've actually ported some of the code from Royale's MXML compiler to Haxe to make it work, and it will have an extensive test suite to ensure compatibility with MXML. I don't have any timeline on when it will be available yet, though.