Love the sound, hate the ergonomics. The good Colonel apparently used a baboon or some other great ape to determine key layouts and the like, as I have never been able to reconcile the way the horns are laid out with the wonderful sound that they make.
I only own one Conn (an artist level alto from the 1920's), and for power and projection, the thing can't be beat. However, the thumb hook is a killer, the table keys are bizarre, and the palm keys are designed for the aforementioned baboon.
If I could do it all over again, I would have at least had the thumb hook replaced during the rebuild. Can't do too much about the rest, however.