Others have probably covered this ground, but I find
it irritating that any time a 'computer model' is brought
up creationists who don't like the implications start complaining
that the program had an intelligent designer!
If I write a computer program that models the thermal
conductivity of various alloys, I am looking at empiracal
data, inferring laws of behaviour, creating a program that operates
based upon the supposed laws of behaviour, then seeing if
my outputs are consistent with what was originally observed.
It's no different for the GP example cited in this thread.
The supposed mechanism of evolution has been modelled, then
applied to the task of circuit design. The resultant designs
show a complexity equal to, and in some cases elegance greater
than, human designs.
If this does not indicate that the supposed mechanisms of
evolution can create 'designs' without any intelligent
intervention I don't know what will!!!