hmmm... too bad. I have yet to try gambit, but I like the idea that it's fast, supports 64 bit systems and along with termite http://code.google.com/p/termite/ there's concurrency model similar to Erlang. Though I am not sure that would even work with arc, but at a faster version of arc with a concurrency model sounds better to me.
I'm just in this investigating/researching languages + features mode lately :)
