Simon - I don't understand your concession that evolution can't be reproduced. It can, and has been reproduced. Obviously no one has gotten a line of chimps to eventually give birth to a human, but there have been plenty of demonstrations that bacteria evolved to better exploit the resources in their environment. That is evolution and it's been reproduced in a controlled laboratory environment. Since we can reproduce it, it's obviously observable.
It also has made numerous predictions that have been accurate. Darwin himself predicted the existence of a moth with a super long tongue based on his observation of a flower that had an extremely long tube leading to it's nectar. This prediction was later found to be true. There have also been lots of predictions in the areas of genetics, embryology, paleontology, psychology and other fields that have been shown to be accurate.
It's funny that even a cursory look at their argument is all that's needed for it to fall apart. Also, by their criteria God doesn't even qualify as a theory...