I really like it. It's yoghurty but sour and sweet... which sounds really disgusting but it's actually good. I have millions sometimes, in taiwan you can even get slushies in yakult flavour and big bottles of them and it's just like a normal drink. It's definitely an acquired taste.
As for the special bacteria stuff, it's just like yoghurt. Helps the um... sorry I don't know the word... the "eating" system (like the cardiac system, I don't know the word for intestines and stomach and that!).