I just bought Scrivener for mac and only have previous experience with Celtx from back when they were new and independent. I recall how smooth that program was with the tab features giving instant access to the multiple intuitive text changes needed for screenwriting flow. Scrivener has the features in place, but for me they are toggling back and forth between working and not working. Sometimes when I enter-tab it goes to the correct function immediately, i.e.writing some dialogue, then enter-tabbing to either get another character heading or an action entry. I’m at about 50% workability right now - the other half of the time it just doesn’t want to do it right - so I have to manually change to the selection necessary. This defeats the purpose.