After reading through all the posts, I totaly agree that it not science at all to depend on swd/ift in sciatica. If we were to concentrate on finding the cause of sciatica and release the patient of it, pain relief automatically follows.
As someone has written in one of the posts,

I am often frustrated by physios who look down on certain modalities, while maintaining that their particular approach minus modalities is the only one that promotes "professional status". These people, in my opinion, are focused on the diagnosis and not on the holistic treatment of the human being in their care.
it is not looking down on certain modalities, nor is it that our particular approach minus modalities is the only one that promotes "professional status". It is not that we are focused on the diagnosis and not on the holistic treatment of the human being in our care. If my treatment is backed by a good assessment, I do not need any modality to bring relief of pain to any patient. In fact since most of my patients are direct contact patients,I make it a point to tell them to come for their assessment & their sessions without taking any NSAIDS. This lets me know exactly what effect my treatment has had on the patients symptoms. I emphasise on modality on those patients who are a little sensitive and equate the time spend at the clinic to the price they are paying , and do not concentrate on the relief obtained. In these patients again I give the modality according to what is most convenient to me at that point of time.
Regarding alophysio's comment that the therapist never knows if the machine they are using is actually working or not, I think that would be unforgiving. If I do not use my U/S for a period of time, I always make it a point to test it before administering it on a patient. Even if we use the modality for a placebo effect, one must see that they in working condition.