Tone: Definitely old-school pure drop. A wee bit raspy, and very bright sounding. But, as I mentioned above, it wasn't raspy enough to annoy me. I really enjoy the sound of this whistle.
Volume: Louder than expected. It's not my loudest whistle by far, but it's louder than any of the inexpensive whistles I own, and I think it'd stand up nicely in a medium sized session. Unfortunately, it doesn't really hold up in my truly rowdy Sunday session--if I'm starting a tune, I have to switch to a louder whsitle so the other musicians can hear what I'm doing. Though if I'm not the one starting the tune, it still blends in nicely there.
Responsiveness: Extremely quick and nimble. This whistle can do anything I ask of it, crisply and effortlessly rolling off ornamentation as quick as I can play it.
Tuning: With the tuning slide all the way in, this whistle is 45 cents sharp. All the way out, it's 30 cents flat. That's an awesome range, and more than most people will ever need. The whistle is in tune with the expected breath requirements, increasing slightly as you go up the range. The A and B notes require a touch more push to be in tune, but it's nothing extreme.
C-natural: While this whistle has been compared to the Sindt, there's an important difference: The OXXOOO C-natural. The Sindt whistle is notoriously sharp here, and you have to half-hole that note. My Killarney is only 6 cents sharp with the standard cross fingering, and you can bring that under control with your breath, OXXOXX brings it down another couple cents. Since it's so close, and can be managed with the breath, I already like this whistle much better than the Sindts I've played, because I don't have to retrain myself to play those notes.
Hole size and placement: The holes on this whistle are fairly medium-sized, and are centered nicely on the body. As with many designs, the E and F# holes are closer together, but they aren't so close that my chubby fingers touch when playing this whistle. It's a pretty typical configuration, and I had no issues just picking the whistle up and playing from the get-go.
Air volume requirements: On the low side of average. I picked the whistle up and played it for a good 90 minutes when I first got it, and didn't find myself gasping or running out of breath in odd locations.
Air pressure requirements: Also on the low-side of average, as far as high-end whistles go. It takes a little more push than some of the inexpensive models (like Generation, Oak, or Clarke Sweetone), but not much.
Clogging: Very low. I played this whistle for an hour and a half when I first got it. I didn't warm it up first, I didn't treat it with duponol. I can't smell duponol or soap in the windway, so I don't think the prior owner treated it either. But I didn't have any clogging issues at all. I attribute that to the mostly-Delrin construction in the part of the mouthpiece that channels your breath.
Wind Resistance: Surprisingly good. It was able to stand up to a soft breeze, and only really started to cut out once the wind got a little stiffer. I was able to adjust my body slightly to bring the sound back, but never had to actually turn my back to the wind.