The block/charge call has been probably the worst officiated call in college basketball since I have been watching, and although the semi circle was designed to add help for the referees, it merely added more confusion as referees resorted to merely looking at a player's feet and if they were outside the circle it was a de facto charge and inside it was a block. Not only did it not help, it made the rule worse and was one of the bigger things surrounding the lack of scoring and sloppy play.
Fortunately, some changes are coming. Previously, the refs were not instructed to call a charge unless the defender was in a "legal guarding position by the time the offensive player lifted off the floor", which led to a lot of defenders being able to slide under players who were already going into their shot. But now the defender cannot slide under a driving offensive player "once he has started his upward motion."
The new rule is a bit more subjective, but it puts the onus on the defender to get there, rather than the offensive player to avoid the contact, which is how it should be. Hopefully referees realize the intent of the rule for what it is: an attempt to open up the game and increase scoring, as well as an attempt to keep players on the floor and not remove them from games due to dubious charge calls.
Of course, nothing changes unless the referees call it differently. But if they start calling anything borderline for the offense, fewer defenders will needlessly slide under a player going up for a layup and scoring should increase, the play should be much more open and continuous, and there is less risk of a needless injury. Sounds like a good deal to me.
Now to get rid of that damn semicircle