I confess that I've never read the original sources of the Hayek vs. Sraffa debate, and suspect that it would be worthwile to do so. But I was never convinced that they would overturn or seriosuly challenge my existing understanding of Austrian business cycle theory. I recently read two accounts of the Hayek vs. Sraffa debate, and they validate this.
The first is Bob Murphy's "Multiple Interest Rates and Austrian Business Cycle Theory" (.pdf) He spends several pages outlining Sraffa's critique of Wicksell (and thus Hayek), several more pages discussing Hayek's response, and then even more on Lachmann. He essentially upholds Sraffa's point that in a world of multiple markets there is no singular natural rate of interest - "the" natural rate is a function of whichever good one arbitrarily decides to use as a numeraire. Murphy attempts to solve the problem of whether or not a natural interest rate exists in a barter economy by appealing to a concept of dynamic equilibrium. To be fair he credits Hayek with the basis for a dynamic, rather than static equilibrium construct, but he defines it as the following:
Austrians... should define a dynamic equilbrium construct where quantities, prices, resources, technologies, and even "spot" consumer preferences can evolve over time, but in a perfectly predictable manner
But in 'Prices and Production' Hayek cites "correct anticipation of future price movements" as one of the three criteria for neutral monetary policy (others being constant total income stream, and perfectly flexible prices, see p.131). This struck me as a solution in search of a problem.
In "The Clash of Economic Ideas" Larry White deals with the Hayek vs. Sraffa debate a lot more quickly. He says
Sraffa mistook Hayek's goal, which was not to replicate all the properties of a barter economy, but simply find a monetary policy that would not drive a wedge between savings and investment (p.92)
Isn't that the nub? When Austrians talk about "the" natural rate of interest it isn't because there is only one interest rate, but that there is one particular market that matters for intertemporal coodination. The market that bridges savings and investment. The market for loanable funds. Murphy's 40+ pages of text fail to mention "loanable funds" at all.
Sorry Pierro, but I still don't see what the fuss is about.