I, too, was expecting something of the quality of Mythbusters, and was generally disappointed by Smash Lab. The one episode I have watched has the crew trying to use Aerated Concrete to prevent run-away vehicles from crossing the median on a divided highway and hitting oncoming traffic. They begin by driving a vehicle into several stationary cars to show that that sort of accident is bad (I guess we didn't already know that) and used the pretense that they wanted to determine the GForce affecting the car during the accident. Any data received from this experiment would be useless because in a real accident, the target vehicles (those in the other lane) would not be stationary, and the momentum of those vehicles would have a huge effect on the results. More accurate data could have been ascertained using a pencil and paper far more cheaply than the 6 cars they destroyed.
OK - The crash is good for TV, though, and it is their big premier, so they want to do something big. I can let that slide. Unfortunately, none of the science in the entire episode seems any more reliable or useful. They never mention any attempt to calculate the strength of the aerated concrete, nor do they attempt to calculate the PSI generated by a 4 ton car traveling at 60 MPH (figures referenced frequently in the episode). They only allow their concrete to cure overnight, which would leave it very weak compared to it's 28-day-strength.
I think they would have been much better off stringing together several clips of crashes and explosions, and omitting any claim to science. I still may have watched it, but would not have been disappointed because I would know what to expect.