Thomas Grill:
Once these issues have been resolved i'm very positive that CLR/C# can be a full-featured and performant cross-platform alternative for PD externals (including the dynamic scripting possibilites of IronPython).
Well, although there are currently various quirks involved using the snd external, let me just add that the snd external compiles signal processing scheme code into very effective c code, and is very competetive performance-vice. (non-signal processing scheme code running inside snd is a completely different story though...)