Well, years ago I had a friend get me on herbalife and I had these protein shakes that were meal replacements. it was for weightloss...but I gained 20 pounds. not sure if it were fat or muscle so thats why im hesitant on what my coworker told me... =/
As far as any post gym snack goes, if your trying to lose weight you still nedd to watch the calories. If you consume too many calories no matter what they are (carbs, protein, fat, whatever) you will gain weight.
So by all means, take a drink, just make sure you account for it calorie wise.
And as far as I know, its important to replenish glycogen as it prevents your body from slowing down. If your trying to lose weight, be wary not to overeat, having glycogen is important as it helps your body to function properly. Its been said (on here and elsewhere) that if you don't have enough glycogen your body starts to eat its own muscle as well as its own fat. You need to lose weight by having your body do this but only to a certain extent. If the glycogen is too low alot you can fall into starvation mode and starts to get rid of the one thing it sees as wasteful: muscle.
Being that to have muscle takes a lot more calories to look after then body fat. If its concerned there is a famine its going to favor using calories from muscle rather then from fat Its all stuff I have read and understood, its not so easy to explain as its not something I question as it just makes sense so if you do have questions I'd advise speaking to a specialist or researching for more, it made sense to me anyway. advice.
However 'starvation mode' is one of those contraversial things which some agree with and some don't. Guess its up to you to decide what you go with.
So my advice would be to watch the calories, eat wisely but try not to allow yourself to become starving, replenish some glycogen (theres no reason to overeat, just keep within a sensible calorie deficiency) and also some protein as protein is required to rebuild the muscle you may have torn down during exercise. The body does not store protein so its important to keep it updated especially after intensive exercise when its been under more stress then normal.