Not much To an extent it legitimizes cheating by permitting a person who has done little to receive the same credit as the person who has learned much. When a group is carried by a strong student, it encourages other students to rely on that person rather than to dig in for themselves.
Some students react negatively to the fact that they can no longer fake it.
It is hard to break the passive mode. Waiting for someone to do the hard stuff for you. Study time is to be avoided. I noticed none. The students with weak backgrounds like to hide in Math classes.