From Golf Magazine  (April 2011)
Category: Tour Irons
We tested: 3-PW with True Temper Dynamic Gold steel shaft; 3-PW with FST KBS Tour steel shaft
Key Technologies: "Stabilizer bars" in the cavity are narrower in long irons for a higher ball flight (and faster ball speeds) and wider in short irons, for a lower flight. Varying the depth of the tungsten toe weight—shallower in long irons, deeper in short irons—has a similar effect on ball flight.
OUR TESTERS SAY: Pretty good combination of performance and feel, despite a look that's quite different from traditional Ping irons.
PLAYABILITY: Testers have success maneuvering shots; some rave about control on knockdown shots.
ACCURACY/FORGIVENESS: Help is available directionally and distance-wise on mis-hits; a distinct lack of sidespin.
DISTANCE CONTROL: Comparable distance output (and control) compared to testers' current sets.
FEEL: Forged-like feel on solid contact, with "cast-like" forgiving feel on off-center hits.
LOOK: Inspiring blade-like appearance with thin topline.
Some testers tend to hit too many thin shots; a few find that the light heads require an adjustment period.
From Sports Illustrated Golf +  (February 7, 2011)
The blade-style S56 appeals to players who put a premium on shot control. The steel-body design has variable tungsten toe weighting that positions the center of gravity for higher-launching long irons and more penetrating trajectories in the short irons. The patent-pending Stabilizing Bar Technology varies in width throughout the set to optimize each iron's center of gravity. The machined face and grooves ensure consistent performance and precise control.
From The Shop Blog  (June 15, 2010)
During the Waste Management Phoenix Open in February, several Ping staff players had a chance to see and try clubs the company plans to release later this year. Hunter Mahan liked the company's yet-to-be-released S56 irons so much he said that he'd put them in his bag that week. Unfortunately, the S56 irons hadn't been approved for play by the USGA at that time, and Ping was not ready to release the clubs to the world, so Mahan (who won that week at TPC Scottsdale) and other Ping pros had to wait ... until now.
Ping brought several sets of S56 irons to Pebble Beach this week; the clubs are an updated-version of Mahan's beloved Ping S57 irons and feature several of the same design features.
The S56 irons have a compact head, minimal offset and only a touch of perimeter weighting. A weight cartridge nestled behind the face absorbs vibrations and allows Ping to adjust the swing weight of each club to match a golfer's preferences.
And like the S57, the S56 irons also feature a tungsten weight in the toe area to extend the sweet spot that direction. To help maintain balance, Ping lengthened the hosel of the S56 (thereby adding weight to the heel area), which also broadens the sweet spot in that direction too. The result is a slightly more forgiving blade that will still allow better golfers to carve and shape their shots.
According to Matt Rollins, a PGA Tour rep for Ping golf, the sole of the S56 has been designed to work more effectively through the turf — a feature that tour players who hit the irons in February all noticed and liked.
Don't look for the S56 to add yards to your game. Like other iron sets designed with accomplished players in mind, they were built with an emphasis on consistency and accuracy instead of power.