They give more talk to controls and scientific method than they used to, and they make more of a show of consulting with people who know what they're doing. They do still sometimes do things for the sake of good TV. But in the first 3 seasons or so, sometimes they'd do entire segments that really were just for show and didn't prove a damned thing. They used to have to do revisits 2 and even 3 times because they just didn't think things out, or didn't have anyone on the set that actually knew anything about what they were trying to prove.