I think that you are asking about tone production, and not key work. On my bronze tenor, I have had some minor problems with tone production on the low notes, but I think it is just lack of embouchure support, as I can hit the notes if I add more support, and it is always improving over time and after playing with the setup (I think it is sensitive to mouthpiece/reed combination). I checked with a light and didn't find any leaks.
Now, I am wondering, however, if anyone can comment on how the
key work compares to more expensive horns. Specifically, I find that I can't make a completely smooth transition with the left hand pinky keys by using only the rollers, but I have to actually pick my pinky up slightly to move between the keys (it's as if the keys are too far depressed or something, so that when one key is depressed, its roller is too far down below the roller next to it).
Having said all that, i want to mention that this is an amazing horn!. I ordered my bronze tenor several months back from
http://www.woodwindandbrass.co.uk/ (service was excellent by the way), and the more i play it, the more I enjoy it and realise how much potential is has. Others have commented on the build quality, so I'll just say that the response is great, whether playing softly or loudly, and it gives me a rich and wonderful tone (and, this is all with just a Rico Royal Graftonite!). Now I'm guessing that if you put a professional horn from one of the big makers in my hands, I would be even more impressed, but truthfully I just really enjoy playing this thing and can't say that it limits me in any way, currently or probably for a long time to come.
If I had to come up with a complaint, the upper A is "noisy/airy", with the noise coming from the neck octave key vent (if I play upper A without the octave key, it is a completely pure sound). I don't have a solution for this yet (does it affect other tenors?) Oh, and a couple of corks have fallen off, which I easily fixed by cutting some new pieces of cork and applying them with rubber cement.