We did it in 2010 and it's an easy journey. When you get off the train at Harwich, you can just roll your luggage to the ship. I recall the return tickets were much cheaper than singles. Choose carriages in the front because at one particular stop mid-way there's announcement that the train would continue its journey with only 4 carriages and we had to move our luggage to the front. Not sure if this is still the case now. Otherwise, the journey was easy and hassle-free.