I used to have this instrument a few years ago until the F attachment started to get stuck. I tried everything the internets could come up with and followed every instruction properly, but it just stayed stuck. I sold that instrument and I actually wasn't all that impressed with the tone, especially when you compare it to a Bach 42, but...
Now that I know what kind of tone I want and what mouthpieces are suitables to those ends, I got this instrument again and with the JK Exclusive 12E, large shank. The standard mouthpiece with the deep round cup makes the instrument sound held back, reserved and boring. With this JK however, the tone is much clearer yet quite sonorous when you put some appropriate lung capacity into it. I now use it in a local fanfare orchestra and it just works miracles. It sounds absolutely impressive and in my opinion, as long as you use the right mouthpiece, you can actually compare it to a Bach 42. If I were to take price as a quality, then I would certainly prefer this instrument over the ludicrously expensive Bach.