I've tried a lot of weight gain supplements and have found that many of them end up tasting chalky, thick, chunky, or just plain terrible. Cytogainer actually tastes really good, which means that I'll actually use it (some other products like Serious Mass I couldn't stomach after a few servings).
The problem with this stuff is that it is very expensive, so I typically use half a serving mixed with an egg and some penut butter (take 2-3 times a day) - still get a good solid shake but it lasts a lot longer. Also, sometimes its good to change up the flavor and add chocolate or strawberry milk mix. In terms of results, it does the job in that I can have a couple of shakes a day in between meals to up my calorie intake and gain weight. Also, Cytosport is pretty good with displaying a lot about their products on the packaging wich makes me feel a little more confident that they are not putting anything in there that is a banned substance (NCAA or other).