From past experience they don't tell you anything you don't already know (if you are at all handy). 

We just paid $600 for a building inspection in Christchurch which uncovered popped nails on the roof. 

We also sent in an electrician who discovered 2 lots of illegal wiring, a plumber who found 4 leaks under the floor, and we had a free drainage survey which discovered earthquake damaged earthenware. 

None of the stuff we asked the vendors to fix before settlement was noted in the builders report....

I've got no choice in that my current insurance company has asked for an Earthquake damage property information form to be completed by a building inspector (or registered master/certified builder). We were going to get a building inspection done as I have found the information provided previously was useful, however the person I used previously is no longer in the area.