Found this neat little video on You Tube that explains Actor Network Theory in plain english (though I think Latour does a pretty good job of explaining things in easy to understand terms himself).
Some of the criticisms she mentions are (via Wikipedia):
1) That it insists on the agency of non-humans which lack intentionality.
2) That it is amoral
3) That it doesn't account for structural factors (i.e. power, class, scale, etc.)
4) That it's merely descriptive
Responses to those criticisms (partially from Wikipedia, partially my own):
1) ANT doesn't imply that non-humans have intentionality. It doesn't claim that intentionality is a characteristic of agency. It doesn't locate agency in humans or in non-humans, but in heterogeneous associations of humans and non-humans (i.e. Actor-NETWORKS).
2) Morality and politic positions are possible, but you have to describe the Actor-Network first. I'd actually argue that ANT is inherently political as it deconstructs concepts such as power, class, scale, gender, etc (see #3 below) and highlights points of intervention.
3) People - critical scholars especially - tend to throw around terms like Power without explaining what they are. This has been extremely frustrating to me as I try to understand exactly what it is we're trying to resist and the best tools and techniques for intervening. To me ANT operationalizes these concepts in a way that few others have (i.e. Foucault). Again, understanding how these things work directs us to points of intervention that allow us to change the way things are. How can you fight something like Power - which doesn't exist, but seems to determine everything around us?
4) Maybe it is merely descriptive, or maybe it just recognizes its own limitations. More scientists (both natural and social) ought to acknowledge the limits to generalization and prediction that are inherent in their work. The world is full of uncertainty and complexity; if we recognize this fact, then the possibilities are endless!
I also recommend this short article by John Law, Notes on a Theory of the Actor Network: Ordering, Strategy, and Heterogeneity. In fact, I recommend a visit to John Law's website, Heterogeneities, which has a lot of good recent articles. Like Latour, he's a good writer and explains things in a way that's easy to understand.