I recived an o’brien whistle a number of moths ago and have spent that time really playing it and I really have been enjoying it. I have a high D whistle with Derlin fipple plug. The whistle has a great tone and has a low air intake (slightly more than a penny whistle) .I would say that is the perfect upgrade for someone who enjoys playing the whistle but only as a hobby and at $65 is a complete bargin. They are avalible from obrienwhistles.com 
MAtheu
I’m expecting a set of his whistles soon, in exchange for my extraneous Chieftain low D. He’s been a very pleasant guy to do business with, and I’m really excited about the whistles… Especially the C, so I can finally play Sgt. Early’s Dream at the slow session without having to borrow the unplayable cheapy.
I received my O’Briens a couple of days ago. I haven’t thoroughly explored them yet, but my impressions so far are that they are very well in tune and sound very sweet and warm. They are, as people have said elsewhere on this board, very sensitive to the way they sit in your lips, and sometimes I tend to hear two octaves at once when trying to play the 2nd octave, but I think that’s just a matter of familiarity.
My primary use, I think, will be to have a C whistle to take to sessions. The C and Bb whistles are definitely my favorites.
In short, I think they’re very good whistles.