While I think Logic X is pretty darn good so far from my couple of days working with it (flex pitch is outstanding and also track stacks) I have to say I am less than impressed with the arrangement markers. This is the worst implementation of a great idea i have ever seen in Logic. They may work for really simple songs but for complex long songs with many overlapping ideas and parts it doesn't work IMO. They just turn your song into garbage and you are left trying to make sense of what just happened when you move one of them. Also you cannot delete them. They are really quite dangerous if you have one highlighted and hit delete is removes everything under it. Perhaps you can only use them if you begin an arrangement with them. Bizarre really.