In my introductory physics classes (Phys 101 & 201), I try to employ a number of techniques- conceptual worksheets, group problem solving, peer discussion, mini-experiments & demonstrations, and, yes, lecture. The vast majority of ideas come from other instructors and researchers.
Over the years, my FCI normalized gains have inched upward, but stayed within the central portion of the "interactive" spectrum.
Here is a histogram from my class last spring showing students' normalized gains on the FCI:
Despite the fact that the class average gain was 0.48, several students had low gains (below 0.30). In fact, some students had negative "gains"!
At the same time I was asking these questions, Vince Coletta was doing the same. Since those early stages we've collaborated on of this project.