ImageMagick can read xcf files using delegates for quite some time, btw. Of course, gimp must be installed for this to work.
Right, you could have always done this - but it would have meant having GIMP and temp files.
gimp should be able to save .miff files, too, although I am not sure how tested that is.
saving of .miff is better than GIMP's reading of them. It can only handle about 50% of features in MIFF.
Leonard