When I started up my 15 gallon, I used about half live rock and sand from TBS. I have not had any serious uglies, granted it's only been six months. I was cycling my tank before the rock came to me, and I was just starting to get a dusting of diatoms, but those went away a week or so after the live rock went in. There was some cyano living about half way down my sand bed along the glass, but I haven't even seen that in a while. But I got tons of feather dusters, micro brittle stars, sponges/tunicates.
When I see other people have lots of problems, I have to think I made a wise choice. I am not so smart or so experienced that I can chalk my lack of uglies to husbandry.