I think that storebought kefir tastes more like thick yogurt (which I like by the way), whereas homemade kefir is more like slightly sour yogurt, and they do have slightly different texture. Storebought kefir is very homogenous (which seems to be unnatural to me).
I got my grains last week, and started making kefir right away. I drink kefir like 1 hour before I go to bed.. So it is the last thing that enters my stomach. And now I have healthy bowel movements every morning!