Tom Forster showed this to me (also on Forster's Gym Smarts video, "Inbar Work", the same concept is demonstrated with a more standard floor bar that has rounded edges on the top ends) and I've since had 3 made for my gym, with two of them not completely octagonal on the ends.
I'm still playing around with the value in this piece of equipment and not sure how much actual carry over there is into real giants and ingraining a sense of wrist shift. It's taken my 5's/6's a bit of getting used to (we started on inclined cheese mats) and they should be spotted until it's clear that they understand that they have to push out through their shoulders to end up on top or behind the bar (as opposed to finishing shoulders leaning in front, planched- makes for some).
As of late, I've started adding an 8 incher behind so that they back extension roll handstand or 3/4 handstand/simulated giant to land flat stomach.
*UPDATE June 19, 2011*
Tumble Trak is now selling these as "the Forster Bar".
One problem for coaches to be vigilante on, is the tendency for the chest to go out when trying to roll over. This has a lot to do with the relationship between the athlete's physical strength and the height of the octagon bar off the floor. It's extremely hard to discipline a locked-in rounded-candle shape and apply the right amount of pressure with the right muscle groups to get the body over without wriggling it.
The likelihood of losing shape lessens on the cheese wedge, though.
When I returned from Colorado, I had Jaime (former UCLA gymnast who happens to be the uncle of a former SMGC team gymnast whose father owns the cabinet-making business next door) construct a couple of octagon bars for me and the gym.
