i used it too (there's another thread about it here somewhere). it helped me kick start my weight-loss, i went from 80kgs to 76.5kgs in about 6 weeks.
as the above posters have said, it will only give you the runs if you eat fat. i did find it really uncomfortable (and occasionally scary accident wise), but seeing the 'results' of fat consumption really makes you want to stop eating all that fat!
btw, if you are not eating fatty foods there is no need to take the xenical, addicted2food. my doctor told me to only take it if i was eating fat, otherwise you are wasting your money a bit..