PLCs seem to be the latest fad in professional development activities, and many many others have come down the pike in the past few decades. There is certainly nothing wrong with the idea, but of course, it is all in the implementation and organization as to whether it will be effective or not. Often times our staff meetings will include nuts and bolts information at the beginning, and then the Principal will say, "OK, the rest of the time is for PLCs" with no framework or plan to use the time, and no notice for us to prepare something on our own.
I think a mentoring atmosphere that is more organic in nature is more effective at helping teachers new to the profession. If an administration can create conditions (time, funding, opportunity) for that kind of mentoring to take place, I think it would work better than formal PLCs.