@Hugomack
So far, my experience in rehearsals has been good. The acid test will be this Saturday. First gig with the FM9.
I don't notice any issues with changing presets utilizing the Setlists/Songs functionality. It certainly opens up possibilities for Preset and Scene combinations that change much faster than I could do punching the foot switches manually. I don't make a lot of Scene changes in the middle of a solo. I am the rhythm player in our band and so I have not had any issues where say for example I need to change to a scene that has a different amp on a different channel and it causes a small obvious gap in the music. It is my understanding that this is where you can have the longest delay while the unit loads the new amp and channel. But even these changes are relatively quick in my experience. Fast enough that I can make the change during a "silent" gap in the song between chord changes. YMMV depending on your playing stile and music.
The one thing that I don't like that I have had to get used to is with the supplied foot switch Layout. The mini-displays under the switches show you the Previous Song and the Next Song, but they don't show the Current Song you have selected. This has taken a bit of getting used to. You can get the current song to display momentarily on the main screen by pushing any active Scene foot switch, but you have to be alert or the display turns off and you miss it. I am getting used to this, but it sure would be nice to have the current song displayed some place so you are not trying to figure out where you are in the Setlist. There is probably a way around this, I just haven't figured it out yet.
Good luck with your FM9. I think you will be very pleased with it. Have patience, it is a complex piece a gear. But it is well worth the time invested. It sounds great and has a lot of functionality that Fractal is constantly improving.