The prohibition on borrowing makes it very impractical to have property in a super fund, unless you set up some really tricky complicated structure or have really large amounts of money.
I don't have a disagreement with the current scheme. My objection is to Keatings scheme to increase the total contribution from 9% to 15% or more. For most people, the effect of that would be to crowd out the opportunity for any non-super savings and investments, which is bad thing.