I am using the FX100 live. I have a printout of the factory presets in case mine on bank 1 go south. Only issues so far have been not being able to update the board with my iPad without a wifi connection and some random starup weirdness. I can change the preset on my iPad, but it will not update the board unless my iPad is connected to the Internet. My solution has been to use my iPhone as a mobile hotspot. Some venues have had pretty shady cell service, but so far, so good. The starup thing is that the FX100 will sometimes startup with some other preset on bank 1A. I suspect it is the factory preset persisting. The solution is simple, just press a different switch then switch back. Just odd is all.
I run it through an old Roland RG-90 and it sounds fine, no complaints. We ran it straight to the PA once to see how it sounds and it sounded great. Might run it that way in the future if we get a bigger board, (not enough inputs right now).
My overall feeling is that it is not ideal, but it works fine live. I work on my presets at home or well before the show so there are no surprises. If you like to fiddle while you play, I'd say get something else. If it is a matter of getting the right sound for things you perform regularly, I'd ask if you could prepare a little better before going on stage.