Has anybody used a TENS machine? (TENS stands for Transcutaneous Electrical Nerve Stimulation). I have read about them on the internet and in magazine articles. I am considering purchasing one for shoulder/neck aches & pains (possible fibromyalgia or arthritis) and would welcome the views of anybody who has used one. Did it work? Should I pay a high price or just opt for one of the affordable ones? There are many sizes and shapes on the market but from what I've seen it seems to me that one for about 50 Euro would be as good as any other, but am I right or wrong? Thanks for your help.