I’ve owned a Howard low D for about 9 months now, and I’ve been fairly pleased with it-- really nice tone, and not incredibly expensive. The holes may be a little larger than average, but with a little practice, I think anyone can manage. You really have to put a lot of air though to stay stable in the upper half of the second octave (it tends to flip back down easily), at least on my whistle, anyway. I guess that would be my only complaint though.
Cheers,
GeoMan
Here is more:
http://chiffboard.mati.ca/viewtopic.php?t=15676&postdays=0&postorder=asc&start=15
Brian (bjs)
Dixon lowD
I’m new here (if you discount lurking in the shadows for a few months) but I have a Dixon Low D and have played the Susato Low D, both are easily played … and I have a small hand. I like the sound of the Dixon better. Both were bought through The Whistle Shop – Thom Larson is great! He answers all my stupid questions without a hint of impatience.
But I am waiting for a Silkstone Alloy Low D … Is WHOA terminal? 
I got ahold of one of the $18 practice low D whistles from Jubilee. Since I don’t play in sessions, never plan to, and basically just entertain my family with whistling, it’s good enough for me. It’s possible to make nice music on it. It could also give you the experience to decide what you DO want in a pricey whistle.
Good luck!
i’ve had a susato low d, dixon low d, reyburn low d, a jubilee low d, hoover low d and a kerry low d. reyburn is awesome. love its full haunting sound and by using your pinky, you avoid using piper’s grip. found the hoover could also be played without piper’s grip. quieter than the others. i personally didn’t like the sound of either the susato or the dixon. but the sound out of the kerry is impressive-full & resonate. so if price is an object, i’d go with the kerry.