Slava Pestov, Joe Groff and I are writing a paper about Factor for the Dynamic Languages Symposium, part of OOPSLA. It's a survey discussing both the language design and its implementation, and you can read the draft on the Factor website. The paper is due on Tuesday, and we would really appreciate any comments you have on it.
Update: I've submitted the paper. Thanks everyone for your helpful suggestions! I'll hear back about this July 15, and report here when I do.