Yes I ever tried it, but from experience over the years I have also learnt to make my own meal replacements / weight gainer shakes.
The commercially available weight gainers are full of sugar and its different forms. Usually they are not really healthy. This is what bumps up your calorie intake, so that you are actually consuming more calories than your body burns, in order to put on weight.
You could try making your own shakes as well. I bought a blender for this purpose.
A standard breakfast shake for me would consist of half a cup of rolled oats, 3 tablespoon of black sesame seeds, a scoop of peanut butter, one banana, one scoop whey, one scoop casein, one cup milk. Blend and add water to desired consistency.
You can experiment with different fruits, berries and ingredients to see what best suits your taste, as well as supporting your daily caloric needs.