I've not found it all that useful for the transmission aspect. That 40% cap really cripples transmission to the point where most of my ships dont bother with antennas now. However I have found a use for it when dealing with mun/minmus. I basicly put a lab and a pile of fuel tanks in orbit around the moons. I docked a bunch of drop pods to this arangement. Each pod is little more than a small fuel tank and engien, a command pod and chutes, and a probe core with a solar pannle on it. The main lander goes down, gatheres science and returns to the lab. Kerbal moves all reports over to an empty drop pod. lab resets aplicable experiments. Drop pod is launched back to kerbin while the lander refules and drops down into another biome. Alternitively I can cart all the pods home at once when I'm done with the main mission and skip the fuel tanks drone cores and engiens.