If you want to have a shake for "something different" or keep a few around handy for those mornings when you're on the run and need something super-fast, fine. It's not my thing (I don't like "shakes" or other liquid meal-replacement substances - at all), however if you enjoy the taste and they satisfy your hunger, well... why not.
However, I would caution you about expecting "results" from using shakes or any other "diet" preparation. Having a 300 calorie shake won't be any better or worse for your weight than a 300 calorie bowl of yogurt, fruit and grains, or a 300 calorie plate of scrambled eggs on an english muffin, or 300 calories of Cheerios and milk.
And I would emphasize that you should only use shakes if you ACTUALLY ENJOY them and ACTUALLY FEED FULL from them. If you are choking them down and then starving till lunch, you will end up feeling deprived, "punished by dieting," and it's just a big ole downward spiral from there!
Goal 1 - break 200 (46 pounds lost)**DONE**
Goal 2 - leave obesity behind (BMI 29.9, at 185#) **DONE**
Goal 3 - BMI = Normal (154# or less)
| current weight: 174.0