I did this too before I got married - lost 15kgs in about 10 weeks. I then went on my honeymoon where we had the most incredible food you could possibly imagine and then had back to back pregnancies - all before I got to my goal weight and did the refeeding - so you can guess where that 15kgs is now!!
Jodi - I was going to give it another go but Mum talked me out of it. My particular diet, and I'm guessing most of them, leave you quite low on energy (you are specifically told not to exercise while on the diet) and given my PND and dealing with the girls Mum convinced me that for now at least it was a bad move. It is also pretty time consuming in that everything has to be weighed exactly - not like SS where you can just grab a shake.
If you're interested, I'm more than happy to email you my Cohens diet and the "rules" so you can see what sort of things you'd be up against before you commit to a large sum of money.
I will give it a go again in the future, but for now I think it would do me more harm than good - better if I can just find some will power and eat better, get regular exercise, get some sleep!