I've looked in quite few sources, but I have to admit that Io's
sources seem among the best. It's that easy to understand and follow,
really wonderful
just an example this is the typical DATA declaration
#define DATA(self) ((IoFileData *)IoObject_dataPointer(self))
and this points to the "used" data. That's so "natural" or the nameing
scheme IoMethodTable methodTable[] = {
{"now", IoDate_now},
very simple and clear just have a look at one extension and you
understand how to write it.
I always try to make my code that simple also. Nothing beats this
standard scheme, once you got it you can apply it.
I can not comment on all part of the Interpreter of course but all the
extensions look very clean to me.
It seem also to me that interfacing to C is relativly painless.
Congratulations to all having contributed those fine pieces of code.
Now we'll just need
1) a good book about Io
2) a decent IDE, with a very nice debugger, and best a mixed language
mode (such that one can use C and Io in the same project)
2) Rails or Seaside for Io
4) a decent "resource builder" which one can use for "outlining"
native looking GUIs and/or Web interfaces
ah well just a few more decades of development 
I'm still a ruby "guy" but IMHO Io has this extra edge above Ruby as
Ruby has above the other "scripting languages". I'm starting
understanding it better and better, maybe it's time to write some
"real" scripts in it
Regards
Friedrich
.
