What is Post-Structuralism? And is it any use?

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I still struggle to get my head around the posts (modernism, structuralism, development, Marxism) but one definition of post-structuralism that I like (mainly because it is a metaphor) is as follows. Post-structuralism turns Marx on his head, unearthing again Hegel and his dialectics. Except that now the dialectics have been torn out by the roots and are no longer anchored to an ultimate truth. Instead, they're just dangling in the air competing against each other.

In practice this means that post structuralists no longer want to understand the world (ala Hegel), nor even to change it (in the way that Marx wanted philosophers to do); rather, they want to understand the way we understand the world and, maybe, to change that instead.

The classic charge levied against post-structuralists is that of relativism or an absence of a normative prescription of a world to strive for. Against which most post-structuralists will argue that no they aren't relativists, that not all discourses are equal, and they seek those which are emancipatory.

Me I'm not so sure. To the extent I've looked, I don't find answers to the question "what is good". At least when it comes to outcomes I don't. I do hear normative positions on procedures though. And interesting ones at that.

All of which makes me think that post-structuralism can compliment liberal-analytical or Habermassian (dear god how do you spell that) takes on the world, but that on its own it ultimately flounders. Post-structuralism is like driving lessons that can tell you how better to drive the car but which, at the same time, give you no idea where exactly it is you are going. For that you need a road map.
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Disclaimer 1: There is a nearly 100% chance that I don't actually no what I'm talking about here.
Disclaimer 2: There is a huge variety of thought amongst post-structuralists too. So a critique of one may not lead to a critique of the other.