What other competing propositions?

But this is a side issue, of course, like comparing Sam Harris – not a scientist, and not talking about evolution – with Richard Dawkins, a scientist who actually does study evolution.

The first problem is that "the NDs" don't consider themselves to be the "final arbiter[sic] of truth". They are scientists, though, and do have some pretty strong opinions on what's science. The main political controversy is over what's to be taught in science classes – and there can be debate over whether ID actually qualifies as science.

But maybe scientists really do "set such an artificially high standard that no amount of evidence for ID will ever be enough". The author asserts this, however, and doesn't actually support it. Consider the case of Lynn Margulis who questions key parts of the 'Darwinian orthodoxy', but her latest book has a foreword by one of the key architects of the 'neo-Darwinian synthesis'.
The author asks, "How does experimental science prove or disprove a specific creation method for the universe, given that the laws that govern science only came into existence after the initial creation moment?" That might be a legitimate question – depending on how the terms used are defined – but it's not a question for "NDs", but for physicists and cosmologists. Biological evolution doesn't have any more to do with cosmology than baking or banking do.

ID doesn't make a lot of predictions, and to the extent that ID has made predictions, they have simply not been borne out: http://pandasthumb.org/archives/2008/05/behe-vs-lamprey.html
Finding a structure that really couldn't evolve would be a major problem for "NDs", but none of the proposed examples have stood up to scrutiny. Finding living things with genomes that don't fit into a hierarchical, inheritance-based tree would be another major problem, but even weird creatures like the platypus fit: http://scienceblogs.com/pharyngula/2008/05/the_platypus_genome.php

Philip Johnson, considered by some to be the 'father of intelligent design', understands this: "I also don’t think that there is really a theory of intelligent design at the present time to propose as a comparable alternative to the Darwinian theory, which is, whatever errors it might contain, a fully worked out scheme. There is no intelligent design theory that’s comparable. Working out a positive theory is the job of the scientific people that we have affiliated with the movement. Some of them are quite convinced that it’s doable, but that’s for them to prove… No product is ready for competition in the educational world." (http://sciencereview.berkeley.edu/articles.php?issue=10&article=evolution)

(As to transitional fossils – well, there are plenty: http://www.talkorigins.org/faqs/comdesc/section1.html#morphological_intermediates )