I received my Cillian O'Briain low D yesterday from Steve at Shannaquay. I have had the opportunity to own/play a number of quality low D whistles, and this one compares very favorably.
In appearance and playability it is something of a cross between an Overton and a Burke AlPro. It has the heavier, all-aluminum construction of the Overton. It is more like the Burke, however, in that it is tunable and has a wider airway so that it is not as hard to blow.
The size and spacing of the finger holes on the O'Briain are reasonable. It is not as loud as an Overton, but has a nice tone and mine is well in tune.
Finally, the price is not bad for a higher end whistle, and Steve is a good guy to deal with.
I hope this little review hasn't caused any recovering WhOA sufferers to fall off the wagon!
TerryB