It is not simply and only nasal cleansing. It is a very effective central nervous system stimulation because our nose is the gate to our brain (the nasal tissue contains the parts of brain neurons). Thus Sutra Neti practice can effectively improve the circulation of liquor and therefore nourishment and functioning of all the inner organs. It also harmonizes the right and the left brain.
Combined with Nadi Shodhana pranayama, performed after Sutra Neti, this amazing technique can improve your sleep and assist fighting with sleep disorders. And if Sutra Neti is followed by Kapalabhati (another Shatkarma) — it invigorates (much better than coffee does!) and improves concentration and memory.
It is also one of the best (if not simply the best) means to heal chronic maxillary sinusitis.