Installing Ximian's Evolution can be done. I used Apple's X11 Server and fink unstable to do it. The results were anti-climactic to say the least. The cubic butt-ton of things that need to be installed for Evolution to run is daunting and even when you get it running it feels so out of place in the OS X environment. Even a gtk Aqua theme can't do enough damage control on the interface to make it usable unless you have come from another platform where you were comfortable with Evolution.

An example of what you can expect with a fink install...

The following package will be installed or updated:
 evolution
The following 42 additional packages will be installed:
 bonobo bonobo-conf bonobo-conf-shlibs bonobo-shlibs freetype2-hinting
 freetype2-hinting-shlibs gal21-shlibs gconf gconf-shlibs gdk-pixbuf
 gdk-pixbuf-shlibs gnome-libs gnome-libs-shlibs gnome-mime-data gnome-print
 gnome-print-shlibs gnome-vfs-ssl gnome-vfs-ssl-shlibs gtk+ gtk+-data
 gtk+-shlibs gtkhtml1.1-shlibs guile guile-shlibs imlib imlib-shlibs libglade
 libglade-shlibs libpng libpng-shlibs libpng3-shlibs libtiff-bin
 libtiff-shlibs mozilla-shlibs netpbm-bin oaf oaf-shlibs orbit orbit-dev
 orbit-shlibs scrollkeeper soup-shlibs

I had the bright idea of installing some packages from stable, since there were binary packages and I didn't want to be compiling stuff for a week. This is a bad idea. The library/package conflicts that resulted were a dependancy nightmare. I ended up just letting fink compile/install everything from unstable.

Installing Evolution is a lot like climbing a mountain. Once you get back down, people will question why you climbed it in the first place. "Because it was there," may be the only real answer.