I did that years ago with Slim Fast and it worked. The problem I have with them now is that they simply aren't healthy. Look at the sugar! My lord, it's like having a candy bar. I still lost weight doing it but that was because I was restricting calories but I just can't talk myself into using a product like that now. I'm more into using healthy products.
However, I am about to do a plan where you replace 1 meal a day with a shake but I'm using Beachbody's vegan "**********" which has no sugar and is full of good ingredients. It's on order and I'm just waiting for it to arrive. It gets pretty good reviews so I'm excited to try it.
"A mistake is not failure but feedback. -Rod Gilbert"