I am the co-author of the cooperative REPL servers patch. This patch allows an interactive programming environment to be integrated into applications that are single-threaded and/or run an event loop. I am using cooperative REPLs for a 2D game development engine written in pure Guile.
I highly recommend trying out Guile. The community is really great. I entered #guile on freenode about a year ago when I knew nothing about Scheme and everyone was friendly and helpful. I've since authored 3 patches and written some pretty awesome programs with Guile.
To further entice you to give Guile a try, check out this post/screencast in which I demonstrate functional reactive programming in the context of game development:
http://dthompson.us/functional-reactive-programming-in-schem...
Happy hacking!