They will definitely eat the good stuff too. Depending on your tank size it will also likely starve to death. Most people say don't even bother unless you have over a 180gallon.
That said.. I have one in my 30 gallon, I've had it for 4 months as it was one of the first things added to my tank. The sand bed is still showing signs of being a typical live sand bed (DSB). I guess in a few months I will know if the star has been eating or not *shrug*. I bought it without knowing much about them and going on LFS word (newbie mistake, and info from not one of the best guys at the LFS). Now my gf won't let me get rid of it -.- ... Asking her how she would like to starve to death slowly over 6-12 months didn't help convince her any either lol.
So if you decide to go through with it, best wishes, most will tell you it won't make it. Even with having one, I still don't recommend it based on what I've read.