Cablevision seems to be the largest offender, consistently delivering ~69% of advertised speed. Qwest is another I noticed from skimming the data that consistently underperforms by a significant margin.

If anything, this reads like an advertisement for FiOS. Verizon's FiOS dominates every (positive) metric. I've heard that they've stopped deploying FiOS to new districts. A shame, if true.

Guess I can always hope Google's fiber project goes well and someday sees deployment in the Chicago-land area.