Hello,
Those of you who came to the March meeting may remember that I talked about a spare-time project of mine to catalog the choices that Scheme implementations make. Finally following up on suggestions received then, and succumbing to further prodding, I have posted a collection of preliminary results on the Web. For a good time, browse
http://web.mit.edu/~axch/www/scheme/choices.html
Cheers, ~Alexey
P.S. And let me know what you think!