If you're curious about the subject of "disruptive innovation," as Clayton Christensen defines it, or just thrown around the term on occasion, I recommend The Good Enough Revolution: When Cheap and Simple Is Just Fine," by Robert Capps in the new Wired. "Good enough" means a bit more and a bit less than "disruptive innovation," but this article should get you closer to Christensen's intent than 95% of the things I've read by people other than Christensen. It is a "good enough" definition.
In short, if you can map your internal definition of "disruptive innovation" to the definition of "good enough" this article should impress upon you, you'll probably be better off.
"Good enough," as a term, does a better job for one reason: it is more specific and less cool sounding. Given the discourse of contemporary business literature, "disruptive innovation" might as well be "kick-ass innovation" or "awesome innovation." Everyone who reads about it is sucked into trying to figure out how what they like or do is "disruptive." "Good enough" encourages a more restrained analysis.
For example, K-12 education. Who's up for a new wave of "good enough" elementary schools? No? Looking for a "good enough" high school for your daughter? Didn't think so.
On the other hand, we're in desperate need of "good enough" educational technology, particularly on the hardware and infrastructural side, that is cheap and "good enough." If only we laptops that were "good enough," and affordable for every child, that would be innovative.