I did this hike when I was an a study abroad with a group of adventurous girls. They taught me to love hiking and that is something you can learn to do well. This was one of the most varied and beautiful hikes I have ever done. (I couldn't help pretending I was a hobbit going through the dead marshes and climbing Mt Doom.) We made it up to the crater but did not find the summit. The Emerald Lakes were amazing. I would recommend this to anyone who goes to New Zealand.
Started from Whakepapa chateau at 9am, pass by Taranaki Falls along the loop, then Northern Circuit to Mangatepopo shelter, Mt Doom, Tongariro and finished the Crossing at Ketetahi in the dark at about 8pm. Very unique terrain owing to the Emerald Lakes and Blue Lake.
Note: I had a fairly easy time hitching a ride from Ketetahi back to Whakepapa. This is viable alternative to commercially-operated shuttle services.
Did the traverse twice, once in the deep snow, once in the dry, each a week apart. The most amazing contrast imaginable. The colours of the mineral deposits, the lakes, Lake Taupo in the distance, Ngaurahoe, Ruapehu, just such an overwhelming onslaught of sensory input.