Quote from trader422:
3. Totally agreed, it "should be" ... but I tried out the hidden ISLAND thing, for my NASDAQ stocks, for several days last month and then several more days last week, and I could never tell any difference except I think (not completely sure) that ISLAND hiddens are even more worthless than non-hidden ISLAND limit orders ... I suspect that somehow the HFTs are getting more information about ISLAND hiddens than NYSE hiddens ... obviously not IB's fault; the main problem is that for the past two or three years the HFTs control NASDAQ liquidity to a much greater degree than they control NYSE liquidity.
Can you explain more what happened with your ISLAND hidden orders?