We did an Advocare 24-day Challenge.
The program is good because it gives you structure to kick start your weight loss. It's not cheap, but I think it's worth it for the month or so it lasts. We have pretty much stopped with the products from them, but maintain the eating habits that we adopted. They make shakes that we keep on hand just in case we need a quick meal. And unlike many other companies, their shakes are damn delicious.
I'm not a crazy Atkins or no-carb freak. But we have attained a lot of success but cutting out most white carbs. No regular flour, no sugar, no white rice, limited white potatoes. Instead we eat whole wheat bread, use honey or agave for sweetener, eat brown rice, and eat sweet potatoes more. It's a pretty easy change to make that doesn't require a tremendous amount of planning. Saturday is cheat day where we eat whatever we want.
The problem with natural fruit or veggie smoothies is that they are loaded with sugar and calories from the fruit/veg, even without adding any sweetener. You'll be better off going with a product like Advocare or another premium nutritional shake (maybe Herbalife?) that uses protein and fiber to make you full, but doesn't have much sugar or carbs. Plus they are easier to make and clean up after, and can be made away from home in a shaker bottle.