with any diet you will put the weight back on IF you dont learn how to mantain the weight you have lost, thats why its important to follow a program through to the end.

As far as weight loss shakes go, personally I dont like them. You need to chew food to recognise that you have eaten, even though the calories are exactly the same you still feel hungry. Shake diets need one hell of a lot of motivation and compliance, and they dont allow for you to stray from the program. However I do know alot of people that have lost a lot of weight on shke diets and mantained it for years.

I was told by someone that had lap banding done that Optifast is the only medically recommended shake program on the market, because it has all the necessary nutrients etc. (not sure if thats true) but they are a bit dearer.

Good luck with it, if you have the will power then no harm giving it a try.