I think a lot of critics of postmodernism get caught up in their fear of its outcome - a meaningless and purposeless existence. No one wants to be a lemming. But I think that this pessimistic interpretation of pomo doesn't fully acknowledge the extremely constructive and progressive nature of pomo. If you look at it 'objectively' (I know, I know, not possible), without focusing on the connotations of pomo values, then you can see that pomo has done a huge amount of work in furthering society and our understanding of it.
Personally, I don't think that the fact that pomo deconstructs texts and ideals is a negative thing. The word 'deconstruct' implies a wrecking or ruining action, a negative one at least. But really to deconstruct can be seen as a positive action. It reveals the agendas and discourses within the texts, thus allowing us to gain a fuller and richer understanding of their context, perspective and ideological purpose. When we have deconstructed a text, we can view it from a far less superficial level, because we understand not only what it is saying but also why and how.
In the field of history, pomo has single-handedly taken huge steps to further and advance historiography and historical practice. Because of pomo, historians are no longer able to make sweeping-judgements, and are far more aware of critically analysing a source before utilising it. The role of purpose and perspective in history has been highlighted, which essentially has all added up to far more sophisticated and in-depth history. Of course, if you take the extremist point of view then pomo renders that past completely irrelevant due to our inability to determine how exactly it was. But even this extreme point of view - while not practical - has made historians at least more aware of the use and abuse of historicism.
To say pomo is dead, I think, is pretty ridiculous. Its implications and long-lasting effects are clear not only in history and literature (even now, the most popular children's books often contain elements of pomo - eg. the Stinky Cheese Man, and those picture books where the characters can be seen in the margins, commenting on the story as it goes along). Watch any ad break on TV and you're bound to see at least 1 pomo influenced ad. Even Dead White Males was inherently postmodern, despite how much Williams claims to despise it. Having the characters all step into Shakesperean characters repeatedly during the play was an obvious pomo device which clearly demonstrates how much of society today is shaped by pomo, even if unintentionally.
I guess the most important thing about pomo is how much more aware we are as a result of having studied it. I find myself reading into things waaay too much now. But that's probably a good thing. IMO, whether you accept or reject pomo depends upon whether you agree with the popular saying that ignorance is bliss. If you prefer to remain unaware and simply live life for what it is, believeing that you are not merely a social construct, then that's totally legitimate and pomo is not for you. But if you prefer to look in to pomo and understand it, regardless of what you might discover about yourself and your society, then that's fair enough too, and I don't think it has to be a negative thing.
*takes deap breath and collapses*