This looks like a very interesting book to me. I was, sadly, not able to find much by way of problems (though the sentence of Heidegger's which Carnap made fun of was "Das Nichts selbst nichtet;" the manuscript mysteriously and consistently omits the "selbst"). I did find the very end rather rushed and under-argued; it occurred to me that surely Carnap and Neurath could admit that any statement or set of statements could be incorporated into unified science, but claim that pragmatic concerns made it undesirable to do so with metaphysical claims. This makes the criterion less forceful, of course, but it is not clear that it makes the criterion entirely worthless. In any event, I found the manuscript quite interesting and plausible, and it made me think I should look at some of the material in the Carnap archives at some point. I recommend it to anyone interested in the history of analytic philosophy.