I am able to leave my phone in my office in the basement and walk upstairs to get a cup of coffee and stay on the call with my bluetooth headphones.
Then again, if I'm biking and my phone is in my right pocket and I turn my head to the left, the audio skips. So I don't know if I can blame than on range, but there's something odd going on there.
The frequency range used, 2.4Ghz, is absorbed/blocked by water (rain, fog, leaves, wet dogs, human bodies, etc). Most mobile devices use a fairly weak transmitter both to save battery and because the distance between devices is expected to be short. On top of that, when indoors the signal may be bouncing off walls or other surfaces.
Then again, if I'm biking and my phone is in my right pocket and I turn my head to the left, the audio skips. So I don't know if I can blame than on range, but there's something odd going on there.