Honestly mine was awful. I didn't mind the electric shock part of the test (I've already been using a TENS unit and kinda like the shocks actually) but when the doctor started stabbing me with needles the pain was too much. I started crying and had a panic attack and had to make them stop before the test was complete. I have a huge fear of needles and they didn't tell me before hand that they were going to put needles in me. Only after I was crying and freaking out did the doctor mention they could have given me a sedative prior to doing the test.

I'm not trying to scare you out of getting it done, if your doctor thinks it will help get you better treatment then it is worth doing. But if you have a fear of needles like me you should mention it.