I have a love-hate relationship with this pose.
The love part is it can relieve me of menstrual cramps in a minute, it helps my back when it aches, it wakes me up and energizes me. I definitely turn to it when I have trouble digesting food. This pose gets things moving…
The hate part is that Locust pose immediately confronts me with my weaknesses. If I am lacking stamina one day, Locust pose will tell me. If my body isn't so strong, I can't hold the pose for longer than a few seconds. If there is anger in the background, it is suddenly not so much in the background anymore..!
From an experienced non-partial perspective, this pose is wonderful for building strength, not just in your back, but in the deeper muscles of the core. It also stretches the muscles of the front body, improves stamina and (as mentioned above) can aid digestion...When you perform it correctly! Remember at all times to draw the lower belly in to protect and strengthen the lower back; it can help to imagine someone being able to slip a piece of paper underneath the belly.
Practising this pose every day for a week or two and really building up time you hold Salabhasana will give you great benefits. It's also a kick to suddenly feel you can hold this pose without effort and a certain sense of victory will be yours if - like me - you overcome the "hate" part :-).
Here is a step-by-step description of the Locust Pose.