Poking around the Smash Lab message boards (you need to choose better seed topics, guys), there seems to be a lot of negative feedback from Mythbusters fanboys, who're calling it a Mythbusters knockoff. Which is true. But just because it's a Mythbusters knockoff doesn't mean it can't also be good. It's just that this show isn't very good.
I mean, the Mythbusters pilot was pretty rough and it's a lot different from the way the show is now. But it was still good.
Primary problems with the Smash Lab premiere:
1. It was an hour-long commercial for Rhino Linings.
2. The "car bomb" used 12 pounds of TNT. Even tamping the charge with sand to direct the blast into the building makes it a laughably small car bomb.
3. They showed the effects of the "car bomb" on the "protected building." However, they didn't show the effect of the "car bomb" on an unprotected building. That's kind of important. In fact, without it, it's useless.
As to the rest of it -- some folks are ragging on the hosts, others don't like this or that -- it might get better, it might not. But if they're going to be "solving" problems instead of disproving things that are myths anyway, they're going to have to do a better job.