This is great! I just wrote a similar essay on http://blog.openconceptual.com/ proposing a 'philosophy of enterprise,' which also served as an introduction to the work of Alfred North Whitehead -- a philosopher with a mathematical background who wasn't fooled by the supposed certainty of abstractions:

"Philosophy has been misled by the example of mathematics; and even in mathematics the statement of the ultimate logical principles is beset by difficulties, as yet insuperable. The verification of a rationalistic scheme is to be sought in its general success, and not in the peculiar certainty, or initial clarity, of its first principles."
"The position of metaphysics in the development of culture cannot be understood without remembering that no verbal statement is the adequate expression of a proposition."

Whitehead (who was an early collaborator of Russell's) made these statements while Wittgenstein was a schoolteacher and Russell was still enthralled with his early work, which W. himself later rejected in favour of the ideas he is now (justly) celebrated for.

Whitehead's lack of a legacy in professional philosophy is partly due to the fact that he felt it was nevertheless necessary to articulate a sort of heuristic metaphysical framework -- which few professional philosophers have been interested in tangling with [actually, it's been pretty roundly criticized; I meant that philosophers aren't interested in countering or improving it] (for reasons PG points out in the essay).

By making such an attempt, he has much in common with Heidegger, who has remained more widely read and cited than Whitehead perhaps (for another reason pointed out by PG) because of his esoteric and unclear style. It's as if James Joyce and Kurt Godel both composed universal cosmologies: whose do you think would be more popular among later generations of young philosophers?

Whitehead also agreed with PG's attitude towards Aristotle's impractical metaphysics: "Metaphysics is nothing but the description of the generalities which apply to all the details of practice."

I think PG's "test of utility" has potential, but I think we should be careful not to let it stray too far into an authoritative stance. (... while I try not to stray into "word soup.") What I mean is that, above all, we should be doing philosophy for ourselves but with others, in conversation. We may not get them to "do something differently," but if we can get them to do something with us (like discuss philosophy, as PG's essay has so effectily done here...), then we've done enough (for the moment). I think if we start believing our ideas are for other people's benefit -- that we somehow appreciate their needs and wants better than they do -- we get into hazardous situations of resentment and (ironically) competition.

My favourite "test of the value of any philosophy" (quoting John Dewey) is Dewey's question, "Does it end in conclusions which, when they are referred back to ordinary life-experiences and their predicaments, render them more significant, more luminous to us, and make our dealings with them more fruitful?"

That is roughly a more general formulation of PG's test -- only without the requirement of having someone else read it -- which (correct me if I'm wrong) sort of demonstrates PG's proposal: it was useful in getting me to act differently (or at least getting me to act), which I did by "cranking up the generality" -- to apply not just to written philosophies but any kind of idea or insight. (Now we wait and see how useful my [I mean Dewey's] philosophy is...)

And I fully agree with the last comment: we're just beginning to learn.