> Understood about your objectives, but I think they SHOULD include  
> teaching
> efficient updates.  When MS did this correctly, they did the  
> simplest thing
> that would work, and then separately modified it for efficiency.
+1 for having both:
* simple, intuitive
* and optimized
And for keeping them separate.  Like "this is how you would use the  
beautiful expressiveness of Smalltalk to do it first, and this is how  
you'd optimize it after profiling showed it was too slow."

Sean

p.s. Loving all this documentation!!!  Wish it was there when I  
started ;-)