It's not high on my ever growing grumpy middle aged list of things that I might want to complain about, but if it encourages footfall into the CE cabin by ET pax looking for the toilet then it is somewhat annoying. There are plenty of ET pax that come through even when the curtain is drawn, but I imagine that the number is higher when the curtain is not drawn. In my experience the curtain is almost always drawn, although I've been on a couple of flights where it wasn't.