In his blog, Kyle Gann wrote "My long-term historical doubt about electronic improvisation is the same as with regular free improv: I don’t get a convincing impression that sustained self-criticism is going on, that improvisers listen to each other perform, hear and identify things that don’t work well, and keep refining their techniques to make the music more powerful."
Now I'm undoubtedly more attracted to free improv than Gann both as an artistic matter (that rock 'n' roll clatter rewritten) and as pure temperament, but think he's nailed a major problem with the practice (though perhaps not the underlying aesthetic). So much free improv has attempted a kind of purity where no obvious styles intrude that the whole thing feels static; it's no accident that so many critics have noted free improv tends to fall into either insect twitter or waterfall roar. Frequently there is no feeling that the players listen to each other despite what many reviewers claim ("listening to each other" seems to be a common motif in Cadence reviews). Plugging up their ears or maybe just layering separate recordings could produce nearly the same results. Just look at free improvers' willingness to play with anybody in any context; I doubt you could convince me this is a bad thing but it does indicate a certain conceptual vagueness. Worse is that the results tend to sound so similar no matter what nationalities, background or even date are involved. A French and American ensemble from 1982 doesn't sound much different from a German and British one from 1997.