I absolutely love Flat. Its very user friendly, and frankly their customer service has been great the few times I have needed their help to resolve issues. I still use Finale from time to time while I still can. Honestly: Flat does maybe 90% of what I need for notation. Layouts are not great, and sometimes I end up exporting into finale just to print something out in a better layout. But for simple part rewrites, creating accompaniment files, short excerpts, its pretty darn good. Playback is not as good as Musescore, that doesnt bother me much. Most of these programs have free options so you can at least get a decent idea of what each one does.