I've been drinking the shakes off & on for a few months, and they've worked pretty well. I only have one for breakfast, there's no way I can replace lunch as well, but I stay full for the morning. I do generally have a piece of fruit as well. I've lost 20 pounds the past few months, but that's not just due to having a shake - I exercise and eat well otherwise. But I do think the shake fits in well.
They have lots of recipes, so to speak, different things to add to the shake that are good. Definitely blend the stuff with ice - I don't think it tastes very good to just mix it with milk.
I looked all over the internet for info about it - really the only negative things I found were more about getting into it as a distributor. The product mentions were generally pretty positive. I think it depends on the distributor - I just got mine at a little local shop. They're very low-pressure. I have seen some places recommend loads and loads of different supplements - that gets really expensive and I have no idea if they work well at all.
I'd say it's worth a try.