These discounted tickets are well worth it - easy to exchange and hassle-free! Just be aware that if you have a lot of luggage, having non-reserved seating is a risk you have to take - on the way there, you shouldn't have a problem from Tokyo Station, as it's the first stop. On the way back from Kyoto, you're not the first to board the train and the train is likely to be full already and you'll have to stand. Apart from that, I'd definitely make use of this service again. The 1-day Kyoto sightseeing pass was really handy too!