The paper has been reviewed by two referees both of whom comment on the clear exposition and the novelty of the results. Both referees point to the empirical results as being suggestive of a more incremental improvement in practice rather than a major advance. However the approach the authors adopt is novel and I believe may motivate further developments in this area.
I cannot but agree on those comments! Since we are reducing the variance of the weights, the overall effect may be difficult to spot in practical applications. In the current version of the paper, we manage 20% reduction in the variance of those weights, but obviously this does not transfer to the same reduction of the variance of the overall estimator! Our vanilla Rao-Blackwellisation does not speed up the Markov chain.