I am a week into the use of Alli. I usuallly eat pretty clean 6 days of the week anyways, but I took Alli with meals that had more than 5g of fat in them over last week. On the first day I noticed I had runnier stool but that was about it. I didn't have the leakage like I have heard reported, or have digestive tract pain or anything. After that, I have not experienced any kind of diahrea. I don't know what that means, if it's working or not.
I will not know for another 2 weeks on whether I'm losing weight due to this, but because of my anal nature with recording calories and such, I will definitely report my findings.
I took Alli with meals that had very high fat on my 'cheat day' on the 7th day (last Saturday) and did not experience diahrrea like I thought for sure I would. In fact, it was like it did nothing. I doubled up the alli to 120mg on the cheat meals, too.