This pose is the last pose in the first series of the Ashtanga sequence. Some teachers feel that this pose isn't safe and should be avoided. Someone recently asked me how I felt about this, and I think I could give a better answer than the one I gave initially. So here is my attempt at a better answer.
This pose is not for people who have neck problems. In today's world of computers and cell phones and long working hours, many many people do have neck issues like bad alignment and small range of motion, muscle weakness, etc. This pose is not the way fix those issues. If you have neck issues, then you should not do this pose. You should instead go see a good massage therapist, not just once, but several times. Then you will see the progression of your neck getting better, and you will feel when you are ready to take on new challenges. Then you should go see a good teacher who can explain and demonstrate this pose. When your understanding is sufficient, you will not have any doubts or fears about this pose. If you do have doubts or fears about it, then you should probably not practice this pose.
Also, notice that this pose is the last pose in the sequence. You should do the full first series in sequence before doing this pose. This pose is not for someone to incorporate into their practice if they aren't doing the full sequence first. If you do the full sequence regularly, then you will be able to practice this pose, provided that you don't have neck problems and you use good technique. If you are creating your own sequence of a few selected poses, then this pose may not a good addition to that sequence. When you do a shorter version of the first series, this pose would be one to omit.
The benefit of doing this pose is that it can help prevent you from developing neck problems. If you had neck problems before and then you fixed them with massage, this pose will help prevent them from coming back. You would practice this pose only if you already have the full sequence and do it regularly.
"Yoga And Sacred Geometry" Samuel Palmer's second book.
This book reveals the controlling geometry that underlies the structure of the human body and shows how we can use this knowledge to refine and perfect our yoga practice, gain insight into the true purpose of yoga and become a master of your body. Packed with marvelous full color illustrations.
e-book, 172 pages. 3D Computer generated illustrations.