jlongster I was closely following your blog posts about Gambit-scheme on the iphone and was even inspired to try it myself. However this was shortly before Apple changed the developer agreement to add the "stuff that compiles to objective c is not acceptable" clause.
It appears as you have discontinued this project. Was that clause the reason?
I used Emacs which spawned a REPL connected to a live instance of the app and developed from there. Meaning, the app was running in the simulator/device, and I could evaluate code and instantly see changes.
I have yet to develop much in Chicken, but I've looked at it closely. It works on a different philosophy, one of more practicality (and less elegance). Because of that, it's matured a lot, and it has tons of libraries which is a huge benefit.
Gambit is more lean and portable, good for uses like compiling to the iPhone (that would be much harder for Chicken).
That said, I would probably use Chicken for my next project.