@vidak Chez is the best programming environment and fastest runtime. R6RS has more useful "batteries included", and Thunderchez or chez-srfi provide extra libraries.
Gambit just got updated and it's nearly R7RS. It's very fast, has some nice features & FFI, but it's thin on libraries.
CHICKEN is R5RS+some R7. Huge library support, and it literally is C so adding more is easy. Compiles take forever and it isn't very fast, tho.
Gauche runs everywhere, it has nice libraries.
#scheme