Volume: This whistle plays medium lound. I would expect that in a medium-size session, you'd blend in pretty nicely. Louder than that and you'd be lost completely.
Responsiveness: This whistle is very responsive. I'm able to sneak in ornaments and clips and blips without any issues. The bottom two notes are a little slow to respond sometimes, giving a tendency to squeak if you're playing fast.
Tuning: The instrument, when blown with the proper breath control, is in tune across the range. As mentioned, you do have to push C-natural a little bit. I'm only able to get about a 5-cent variance with breath control, making this whistle very consistent and appropriate for beginners. But it does mean the whistle will lack some of that "soul"...you can't color notes with breath control. The whistle is in-tune with the tuning slide out nearly a quarter inch, giving you a lot of control over tuning to folks who are out of true.
D# (An F whistle's equivalent to a C-natural): OXXOOO produces an in tune D# (an F whistle's equivalent to a C-Natural) if you push it a little with your breath. If you drop any other fingers (OXXXOO or OXXXXO) the whistle goes extremely flat.
Hole size and placement: This whistle has holes are on the smallish-size for a low whistle. You'll have to use "low whistle fingering" to play this whistle. Thus, I'd expect most people to have to use piper's grip, or use their pinkie (as I do) to hit the lowest hole.
Air volume requirements: Low-medium. I can get about 80% through the A part of a reel before I have to take a breath.
Air pressure requirements: Low. This whistle's just very easy to play. Doesn't take much breath, and you don't have to really push it in the 2nd octave, unlike other Susatos.
Clogging: I can't recall any Susato ever clogging up on me. But then again, I've never played one for hours and hours, so I just can't speak to this much. My impression is that they'd be pretty clog resistant.
Misc Notes: You can get susato low whistles with an angled-head option for $20.00 more. This makes it hold more like a sax and less like a whistle, giving you a break on your wrists if you have carpal tunnel or something. This is a neat option.