TubeNet

nitpicking,but, i'd be shocked if it is really nickel plated.silver...

These 621s have an amazing upper register. They are awesome for quintet work, I believe Dallenbach inspired this particular model (or at least made it famous). Unfortunately, because of the bigger-is-better mindset, that's probably why Yamaha is discontinuing this model.

Yes, the intonation is excellent on these horns. The horn is small enough so it easily blends with the other instruments in the brass quintet. It probably provides enough sound for amateur -> semi-pro orchestras and works just fine in larger bands (where there are more than one tuba).

If you're looking for a bass-tuba-equivalent without having to learn a new set of fingerings, this is a good way to go.

I personally feel this is THE ideal quintet tuba. I had the privilege to join the university student quintet my freshman year and used the school's YCB-621S. That horn was so versatile! I felt I could do anything on it and it served so well in the group. I substituted my Miraphone 188 once in a while but it never quite fit. I eventually moved to a YFB-822, but by then my days of quintet playing were slowing down due to scheduling conflicts within the group. If I ever join another quintet who played a great deal, I would seriously consider getting a YCB-621.