I had Xenical, and never ever EVER again, in fact so bad I would recommend people avoid them - my GP said that the main way they work is to scare you off eating any fat in case you require a change of pants, that works better than the fat binding itself at keeping you on the straight and narrow.
I've heard nothing but good about reductil (from family members) and was shocked to see it's been banned, although completely understand if it's dangerous.
I think when it comes down to it, diabetes diagnosis alone has been enough to make me stick to my diet. Although I dont understand how anyone post diagnosis wouldn't feel inspired to stick to a diet, I do appreciate not everyone has the willpower to or will struggle due to depression/apathy, but that's not necessarily something that can be fixed with a pill, to steal another phrase from my doc.
That sounded incredibly smug, it wasn't meant to - I've got at least 8 stones to go, I'm hardly a good example of someone with a healthy lifestyle!