Where I have mine (front of car on hood just where hood meets quarter panel), seems pretty incospicuous, but the head rest would be cool. Does the head rest come off easily (the leather)?
Very easily. There's plastic panel on the back that just pops off (for access to a car seat anchor point, I think). There are two 10mm hex nuts you remove, and then the front and back of the headrest can separate. I actually removed the seatback to run the wires from there, (I'm working on a sub upgrade anyway) but you wouldn' have to do that.
Where are you located? I wonder if you have better satellite coverage.
I'm in Dallas, which I imagine is a fairly good spot. I understand that one of the geostationary XM satellites is at 85 deg W, and I'm at 33N, 97W, which would calculate out to an azimuth of 21 deg E from due south, at an elevation of 49 deg.
But the elevation is the key, since your car points in a different direction for each turn. The idea of the headrest is that it's one of the highest points in the car, and generally isn't obstructed by any solid objects near it - not even people. The only time I lose signal is under bridges or in a garage.