Generally I find that he is on the level, but he has definitely made a few mistakes on his show for sure.
1. He once called Knob and Tube wiring "old aluminum wiring" even though it is actually tinned copper.
2. He once suggested that abandoned wiring should be set up in a bolted short so that it will trip a breaker if energized (that's so unsafe I can't imagine anyone on this board would dream of doing that).
Although, generally, a lot of the stuff he does say and do is above code requirements. I actually have a copy of his book, and he does have a lot of good ideas that go beyond minimum code and really would improve the quality of a lot of construction.
While I am sure everyone makes mistakes from time to time, I do feel he does a lot more good than harm. Especially since on his show he does bring in the proper tradespeople and pull the proper permits. He does do everything through the proper channels with the right people, so overall compared to many I think he's a good role model.