The whelk snails were the only hitch hikers I really hated. The gorilla crabs - I had 2 that got sizable - but by the time they were large (half dollar size body) I was hand feeding them meaty foods and they were model citizens. The pretty much stayed holed up in their general area and never really hurt anything.
Eventually the toadfish that also came with the rock wound up eating them.
Tunicates and sponges only lasted a couple months

- the pistol shrimps that come in are really small and harmless - at least the couple I had were. You'll hear them but rarely see them. I caught a glimpse only a couple times and was surprized at how small mine were. Less than 1/2" for sure and that was after having the rock for several months.
TBS rock is great and I wish I had the space, time & money to dedicate a large tank to a TBS package - the life that comes in with that rock is just amazing.