Fcsh is indeed a lot faster than mxmlc. I've written a small shell script that stands in for fcsh and provides an interface like the standard mxml compiler (mxmlc) so that you can just call it (like you would call mxmlc) and have it return an exit status instead of dropping you into an interactive shell like fcsh does. It's called fcshctl:
> That format may be printer-friendly, but it is significantly less readable on-screen. The text fills the browser window, making each line far too long to read comfortably.
http://hasseg.org/blog/?p=194