I did a lot of searching around before i decided to buy this. There are a lot of low whistle comparisons on youtube which are very useful, but of course cannot convey everything about a whistle. I can't either, other than to give my opinion....which is subject to change because i've only had a few days with this. I do have a basis of comparison though because about four months ago i bought a Dixon low D.
Honestly at this point, i like the Dixon MUCH better. It has an incredible warm tone - very flute-like. it can be played quite softly. it reaches the second octave easily except the high B ... and that's probably just because of my inexperience. And it's physically warm. it never feels cold and hard.
The Chieftan, as i heard in one of the reviews, does need to be physically warmed up. with the Dixon i can just pick it up and start playing. With the chieftan, i need to hold it in my hands, sit on it, put it next to the fire or prepare it in some manner before using it.
I also know why some metal whistles come with plastic/composite fipples (mouthpiece). the aluminum mouthpiece always feels cold.
However, i have a feeling that i will get to like it as i use it. i've managed to get some very nice sounds from it and certainly it's received very good reviews in other sites, and there are a number of very good youtube demonstrations. the construction is also very nice. it looks good and has a nice solid feel(but cold!).
These are my initial reactions. I'm by no means an experienced player. But i think i would have appreciated seeing something like this before i bought it ... especially the bit about how cold it always feels.