I've had mine for almost three years and it responds very well in all registers. I use a rovner dark with vandoren v12 reeds and it produces such a rich dark tone. You can effortlessly play in all registers.
First Impressions: Medium round chamber, straight sidewalls, thick side and tip rails, low rollover baffle into the chamber. Body is slimmer than Selmer / Otto Link, what I'd call the standards. The beak is lower as well and the entire mouthpiece is shorter by a quarter inch or so.
Reed friendliness: Played with Rovner Dark ligature. Reaponds fine with all cuts but tonally works best with harder classical cuts. I liked it best with Rico Reserve 3.5's, they played more colorful down low and smooth up top than Vandoren Traditionals. I'd like to try V12 reeds with this.
Response: By far the fastest responding classical piece I've ever owned; yes, even when including refaced mouthpieces. Tonguing 16ths at 100 BPM is no problem. Feel is even top to bottom. Altissimo is freed up, I got to higher notes than before!
Tonal/Dynamic Flexibility: I find this mouthpiece to be more flexible than any Selmer, however, still has the typical limitations of a classical mouthpiece. The sound can be changed depending on your embouchure, however, I find sounds best with "eu" voicing rather than "ooh". Dynamics are very good but as typical of closed tips with hard reeds, extremely loud dynamics can sound unpleasant if you get lazy. Soft dynamics are a charm, as always. Intonation is surprisingly flexible but can be locked in if using the aforementioned voicing method. In comparison to an S80, the tone is approximately the same in terms of bright/darkness however, is more focused in the core. I still have a large sound, but the core is more well defined in a smooth and medium-dark way. There is less of a tendency for white noise or buzzing. This mouthpiece is also very homogenous in all registers, comparable to my old Rascher's homogenous nature.
Other: There are two notable things that I had to get used to, coming from an S80. The beak is lower, encouraging the "eu" voicing method, think Larry Teal. It can be tempting to bite at first. I found that using a bite plate made the transition easier. Also, due to the fact the piece is shorter, it tunes sharp. Going back to voicing, you must properly voice in the upper register or you will go sharp on top C.
Conclusion: This is a very nice mouthpiece right out of the box and I see no reason to refaced it; build quality is superb. Tonally, the mouthpiece harkens back to traditional French design of the Mule / Teal / Londiex tradition, while staying current with modern demands for flexibility and homogenous sound, which I think is a good thing. This is my new favorite for my classical tenor needs and I heartily recommend it to any student or pro alike!