In reply to Martin W:
Well you asked...
After reading the long and scary list of potential side effects, and finding out that I had to have a liver function test before and during the course due to the risks, I was a little nervous and seriously wondered if it was worth the risk for the sake of a toenail. I started the course with some trepidation on a Saturday afternoon, but when I woke up on Sunday morning there were still no signs of anything untoward, so I started thinking I was fine. I started the day with my usual double espresso, and 10 minutes later I was bimbling around the kitchen when bam! - with no warning whatsoever I shat myself. I thanked my lucky stars that I was home alone in the kitchen and not on the train into work, and I went upstairs and got changed. All was fine until after lunch, when I had my customary second coffee of the day. Exactly 10 minutes later I was off to change my trousers again... So that was that, no coffee for two months. I did try once more after a couple of weeks to see if I'd built up a tolerance, but nope.
So yes, going cold turkey on coffee was slightly traumatic, but I did get my toenail back with no other ill effects.