[Phil]

I really hate to disagree, and take the chance of starting a flame war, but no, not the case. Waves do not magically rotate in propagation. I present as exhibit "A" commercial communications satellites. Transponder 1 and 2, for example, are on the same frequency, but one is vertical the other horizontal polarity. Even after traveling some 24,800 miles from the satellite they arrive in exactly the same polarity they left. There is typically, in the real world, about 20-30 db cross polarization loss. I am a radio engineer so I won't speak to anything specifically involving television frequencies, but the idea they would get into valleys, etc , better doesn't make much sense. Circular polarization is really just a linear plane signal rotating at the carrier frequency. The idea that it would cancel ghosts or eliminate multipath is simply myth. Yes, a circularly polarized signal (which doesn't actually exist) changes the direction of rotation when it reflects off an object is true, but is it going to cancel at the receiver? Probably not. Even if it did, would canceling out the signal (assuming it arrived in the proper phase to do so, which would depend on the length of the propagation path in fractions of wavelengths from the reflection point vs. the direct path, be a good thing? Probably not. If it perfectly cancelled you would receive nothing. A circularly polarized signal is nothing more than a linear polarized signal which rotates at the carrier frequency. Since it is in any given polarity for half the time it is necessary to double the power to produce the same signal from an antenna of any given plane.
As to having twice the watts in the air, again, only true if the receive antenna is circularly polarized and of the same sense, which doesn't exist. For any antenna of single plane polarity, regardless of what it is, the received signal is the same as one radiated from an antenna of matching polarity to the transmit antenna and of the same ERP. That is the point of circular polarization. Regardless of whether the receive antenna is vertical, such as older cars, 45 degrees as most newer cars, horizontal or anything random in between the received signal will be the same.
All FM and TV stations are licensed for a particular ERP so the last statement is just irrelevant.