[well, that was fast... fixed a bug in the tiff-ffi-gen depnedencies. now we're at version 0.2.2]
Some folks have complained about needing to install gcc-xml in order to get the libtiff FFI bindings working. Well, I've finally gotten around to separating out the generation of the xml file and sb-alien file from the C header files from the loading of a pre-existing sb-alien file. Now you can just download tiff-ffi and asdf:oos 'asdf:load-op it directly, without needing gcc-xml-ffi. If you want to rerun the gcc-xml-ffi auto-generation stuff, you can just do:
(asdf:oos 'asdf:load-op :tiff-ffi-gen)
For details see the tiff-ffi project page or download it from http://cyrusharmon.org/static/releases/tiff-ffi_0.2.2.tar.gz .
As an added bonus, tiff-ffi no longer requires UFFI.