While the 50/50 guard has been out there for a while and I'm usually pretty technique-inquisitive, Anthony has been encouraging me to work various other open guards: butterfly (hooks-in), half guard, quarter guard, De La Riva, X guard and I figured that was more than enough to keep me occupied.
He introduced it to most of us in class last night. Simply put, the position is with both of you sitting up. You lock a leg triangle on his near side thigh; he can do the same to you. There is the usual plethora of video clips which are easily found via Google. Anthony said he wasn't a fan but knew he would have to learn the position because guys would be trying it on him and his students in competition.
To me it seems to run against the philosophical grain of what I have been taught that good BJJ is about. My understanding is that good BJJ involves achieving a superior position, so your opponent is put in an inferior position. With the 50/50 guard, you both end up in an identical position, and it comes down to who has the better understanding of the position and can apply it first.
Anthony showed us an entry to 50/50 from where the opponent is on his back and you are standing, and another from a failed legbar attempt, where you keep spinning and end up in 50/50. He also showed us several footlocks - heel hooks are right there, though illegal, so we looked at straight footlocks instead. We also looked at a sweep, and defense against all of those attacks, and a method to pass the guard. All of these would need a LOT of work for me to use them effectively. The guard pass in particular seemed to have large gaps.
Much of the criticism of this guard seems to be that it often ends in a one way or mutual stall on the competition mat, with both guys locked together for minutes with next to nothing going on. You can sweep the guy and then keep him locked up till the match times out. Can you really call it a sweep if the guy is already on his butt?
Love it or loathe it, this is something every competitor will have to deal with at some stage. The continual evolution is one of the things you have to love about this art.