I personally don't like carrying an amenity kit with me simply because its another thing I need to take out of my bag at security and bagging it... in addition to the other gazillion things I need to do (belts, watches, pockets, laptop, iPad yadda yadda).

That said, I read news of some UK ports getting new technology which will result in not having to take out liquids which means I will be more than happy to make use of my existing bags.