CFLs do not present an inductive load like the magnetic ballasts in traditional fluorescent lights. They use high-frequency electronic switching circuitry, which can radiate the noise that blocks X10 signals. With LEDs, there are two basic technologies. Some have a lot of LEDs connected in series, and use a rectifier and current limiter to provide the necessary current. That could be as simple as a bridge rectifier and current limiting resistor. The ones with just several high-power LEDs use a step-down switching regulator to produce the low-voltage high current necessary. They can radiate noise just like CFLs. In fact I have a Lumoform 4W 120V LED light that is the worst noise source I have ever come across. It radiates a very strong signal right inside the X10 bandpass, and even caused a problem for a couple of Leviton switches (with AGC) on its circuit. Because of this, I suspect that LEDs may become even more of a problem than CFLs as they proliferate.