On the general topic here: it seems to me that as soon as the claim is made that the arrangement or organization of a living thing requires a designer, this is a claim that the design is somehow meritorious – it at least is a claim that something good enough to function must be designed, while non-design processes cannot (or, perhaps, only rarely) produce function. So the argument for ID actually IS an argument for “good” design, at its root. Designs work better, the claim goes, than non-designs, and the fact that living things work well is the reason to believe they are designed.
Most of the proponents, too, are not claiming that the designer is some thing or force that has a half-assed wacky approach to design. One COULD postulate such a designer. I have suggested, in other contexts, the idea of PID (Polytheistic Intelligent Design, not Pelvic Inflammatory Disease). Evinrude, the god of outboard motors, convened the gods and gave them a number of bits and parts to work with. Some gods, like Odin, built such majestic creations as the moose. But Gambrinus and Bacchus, on a bender as always, put the platypus together while completely hammered (albeit not by Thor). Such a notion could account for the bizarre Rube-Goldberg-ish nature of living things.
Now, contrast that view with the theology of the typical IDer. These people tend to believe in a singular mighty uber-intelligence, infinitely virtuous and wise. I think that the platypus looks a good deal less consistent with that model, unless the Almighty has an infinite sense of humor to match his other unmatchable qualities.
Now, these same people tend to throw a barrier up here: the Designer, being inscrutable, is someone about whom no inferences may be drawn. This barrier is, I think, unavailable if you are a non-believer or if you are a believer who thinks of God as a force that actually operates upon things in the physical world, and that’s where the IDers are dead wrong: if God runs about editing genomes, popping platypuses out of the ether, and wrestling Irish Elk by grabbing 'em by the antlers, then he is the very farthest thing from inscrutable.
So, why should a god bearing all these superlatives of virtue and peace and kindness go making things like a pancreas so easily subject to diabetes, and inflicting the consequences of that, via Type 1 diabetes, upon innocent children? If we refuse to allow a god that acts in the world to retreat behind the “inscrutable” barrier, we have to admit that he’s not actually very good at this sort of thing, or perhaps he’s a bit odd, or perhaps we have mistaken might for virtue, or some such thing.
So I think that the argument of “poor design” is a good one. It addresses the very rationale for the claim. If one says, “well, designs need not be optimal,” I think one discards forever the idea that the nature of the designer cannot be discerned from the features of design, and an empirical theology is born. That, of course, is precisely what the proponents of ID would NOT want: man’s critical faculties aimed at god, using observations about the nature of things rather than scriptures, with no philosophical fan-dancing allowed to get in the way.