I wasn't arguing that we should all be actually doing Solomonoff induction. (Clearly we can't.) I was saying that there is a somewhat-usable sense in which preferring simpler hypotheses seems to be The Right Thing, or at least A Right Thing. Namely, that basing your probabilities miraculously accurately on simplicity leads to good results. The same isn't true if you put something other than "simplicity" in that statement.
I wonder whether there are any theorems along similar lines that don't involve any uncomputable priors. (Something handwavily along the following lines: If p,q are two computable priors and p is dramatically enough "closer to Occamian" than q, then an agent with p as prior will "usually" do better than an agent with q as prior. But I have so far not thought of any statement of this kind that's both credible and interesting.)
In two posts, Bayesian stats guru Andrew Gelman argues against parsimony, though it seems to be favored 'round these parts, in particular Solomonoff Induction and BIC as imperfect formalizations of Occam's Razor.
Gelman says: