Since they've started online check in, I've used it every time. We've had a room ready for us each time and usually (but not always) where we requested (on our original reservation). Of course, you should have a room ready at that time of day, whether you do it before or upon arrival. As a first-timer, you might just want to wait until you get there and that way you can ask questions and get a full check-in spiel from the CM at the desk.