[plt-scheme] xxx chooses MzScheme as preferred language

Matthias Felleisen wrote:

> When I see the performance combined with the expressive power of  
> MrEd/MzScheme, I will buy it.

In the first lecture of the first-year HtDP-based course I teach, I have 
a slide full of goals beyond "get it working" and "make it fast" -- 
goals like readability, extendability, maintainability, and so on. 
Obviously there are times when speed is the bottleneck and the deciding 
factor. But I suspect we computer scientists tend to make it an issue 
when it is not, simply because it is easier to compare hard numbers than 
the more vague and softer qualities associated with the broader goals I 
mentioned. Does it matter if a given task completes in 10 microseconds 
instead of 50, if a human has to then respond to the result? It would be 
nice to have a path to follow, if speed becomes the deciding factor, 
that does not leave the Scheme universe. But I neither expect nor demand 
that PLT Scheme should provide that path. What it is doing is far more 
important. --PR