Editing builds with too much clutter and MOO is a bit of a nightmare. Live mode can get really laggy on a large cluttered lot. Routing issues start to happen more frequently.
I like the clutter for looks and things like screenshots/sets. It can give a lot of life to the lot and make it looked lived in while also giving a sense of what type of sim might be living there. For regular, every day game play though, I don't use a lot of it and when I use more than my average in a build, I always make sure I play test before I put it into my main save or upload to the gallery.