ASA.....Yes, I have used the Micro Diet (in the 80's) and the cambridge diet, again in the 80's but this one is still going.
You do have to be careful when you are at your target weight with what you eat to mantain that weight, and there is a great risk of putting the weight back on as fast as you lost it if you don't keep a rigid eye on what you eat. In my case, the weight came back to an extent quite quickly on 1.000 calls a day but I came straight off the liquid onto food. I 'yo yo'd' with my weight, using the diet between weight gains, which did me no good at all. When you are on the liquids, about 440 calls a day or thereabouts, your body can think it is in starvation mode and hangs onto everything it gets, so once you give it more food it holds onto it....well at least that what happened to me. However, I see now that there is far more support for this system of weight loss, and weight loss is monitored and in stages, so you lose a certain ammount of weight, then intoduce 'real' food and slowly reach your target, a far eaiser and more natural way which allows your body to adjust to whats happening. Of course, its then what I think is the hardest part of dieting, maintainence! if you slip into your old ways that put the weight on, then of course, whatever plan you took to get there, you will put weight back on. So a good, nutritious eating plan needs to be sorted out for when goal weight is reached, along with exercise. Liquids are a speedy way to lose weight, but if you have a lot to lose remember the skin that has stretched when you were fat also needs time to shrink back, a fast huge weight loss may well leave extra skin folds that you won't like whatever weight you come down to, a slower rate with exercise will help the skin to pull back to the shrinking shape. Think of those that have gastric surgery and lose many stones, they always need surgery to cut the loose skin away.
If I were to go the drinks way again, I would sign up to the total plan and keep going to the counciler. Unless you buy it off ebay thats the only way you can get it. Lighter Life do a similar system, with plenty of help and support. Both will advise you should you have a medical problem, or if you are on medication which means you should not use this method. The advisors are exceptionally helpful online and phone before you start any of these. Whatever you chose....good luck!