I go back and forth on this one. On one hand, it does not really add anything and for a long time I did not really use it. There isn't much point without an appearance system (or a more crucial one). ...
I like a light scattering of things, a pile of books here, a knife block there, a plant in the corner, nothing excessive, but just enough to make the house look like a lived in home, rather than a show home. I hate gallery builds that have so much clutter in them my sims can't move, they are stripped out straight away! There is such a thing as too much, and using MOO is too much! But a little bit in the right places can make all the difference.