Is cranial manipulation ever beneficial?

Absolutely: I do primarily osteopathic manipulation, including cranial manip. (cm), in my practice. Though there are many claims of cm having effects on behavior, memory, etc. (& I have seen some of these effects on children in my practice) i'm mechanically inclined. Cm is extremely helpful for mechanical problems affecting the neck, head (pain), sinuses, low back pain (via its effect on meninges & such), etc.

Cranial Sacral: Yes, can have profound and subtle benefits.