I haven't used Irish rail in ages and see that they have an online booking facility now where you can reserve seats. Is this a good idea or is it better to take your chances on the day ie is the online facility more expensive? I'll be travelling on a Sat and Sun so I'd imagine the trains are busier in those days but it seems I can only reserve a seat on the outgoing journey and can get 'ticket only' on the way back. So does ticket only mean I'll have to stand?