You may not be able to check-in online or at a kiosk -- as these often barf when you aren't on a return itinerary. Keep this in mind if you often arrive at the airport close to departure time as I often do, you may run into issues not being checked in and losing your seat! As a Diamond they always accommodate me (usually with a phone call to the gate). I have the feeling if you aren't Diamond you may get worse treatment.