dirdiff is an awesome little tool. Now that Tiger has Wish 8.4 with the native Aqua GUI elements in it, I had to see how it would run. After a little bump getting the filecmp.c to compile, it works wonderfully. Nothing too complex, just a couple tweaks to the Makefile to handle the mac-isms. Here is the patch just in case you want to get it working for yourself.

diff -urN dirdiff-2.1/Makefile dirdiff-2.1-new/Makefile
--- dirdiff-2.1/Makefile    2005-04-19 05:22:01.000000000 -0500
+++ dirdiff-2.1-new/Makefile    2005-11-27 11:45:02.000000000 -0600
@@ -7,12 +7,12 @@

 # You may need to change the -I arguments depending on your system
-CFLAGS=-O3 -I/usr/include/tcl8.3/ -I/usr/include/tcl
+CFLAGS=-O3 -framework Tcl

 all:   libfilecmp.so.0.0

 libfilecmp.so.0.0: filecmp.c
-   $(CC) $(CFLAGS) -shared -o $@ filecmp.c
+   $(CC) $(CFLAGS) -dynamiclib -o $@ filecmp.c

 install: dirdiff libfilecmp.so.0.0
    $(INSTALL) -c dirdiff $(BINDIR)