The stuff I see at Petco usually looks pretty plain to me. Almost looks like the rounded up some lava rock, threw it in their tanks and upped the price. Im not sure that will ever have much going on. The stuff at my LFS
usually looks totally different. Coralline growing all over and sometimes you can see other stuff (critters, sponges, anemones, etc).
Years ago, I had a reef and it seemed like new stuff was popping up all the time, even months later. I always bought pieces that looked like they had lots already on them.