I used the Scan Diet shakes to help supplement my nutrition due to a stomach disorder for a few months. I did end up needing to have tube feeding which bypass my stomach so I no longer have to try to force myself to drink any shakes for a whle. When I talked to the nutritionists and dieticians (have seen too many in the last year-lol) they all said that for normal situations meal replacement drinks/bar/etc are only recomended for occasional use when it would be possible to eat a proper, balanced meal- never more then a few times per week and never more then once per day. They all made the comment to me that it was unusual for them to be recomending I actually drink more of the shakes but then I was dealing with rapid weight weight loss due to my stomach disorder (and I had/have excess weight to lose) and in the end an extreme solution to give up eating for awhile.
I will say the shakes were okay tasting- just make sure you put 12 ounces of water in like the instructions tell you. You can also mix in fruits to make them more tastey. I actually used them over prepared supplement drinks due to an allergy to corn- the corn based sweetener in them is different enough that it did not effect me.
I would highly recomend seeing a nutritionist or dietician at least 2 or 3 times to help find a healthy way to lose weight- I actually was seeing one occasionally long before I even had stomach problems- it really helped to have someone checking on what I was eating and making sure I had a balanced diet.
Good luck in you healthy weight loss~