Regarding the claim that intelligent design is a "God of the Gaps" argument, I've always found this criticism not only false, but also fallacious and self-refuting.
Critics of intelligent design often accuse ID proponents of using a "god of the gaps" argument, but they refuse to acknowledge that (1) ID isn't a "gaps-based" argument at all since it in fact offers a positive argument for design in nature, and (2), in any event, ID requires no inference to "God."
But there's an even deeper problem with the argument.
Ironically, when critics make this accusation, they are usually committing a "gaps" fallacy themselves. How so? These very same materialists (1) admit that gaps in the evidence for Darwinian evolution exist, and (2) assume that those gaps can and will be filled by materialist explanations. Otherwise, they wouldn't be attacking ID for purportedly filling those gaps with "god." They can't make a "god of the gaps" accusation without also making a "materialism of the gaps" argument -- one that assumes the truth of their own materialistic outlook.
Most "gaps-based" criticisms are flawed in these ways, which is why I try to avoid them. People are entitled to make whatever arguments they want, provided they use positive evidence to back up their position. ID does exactly that.