If you want to experience a bit of most things New Zealand has to offer, this trip is probably ideal for you, although for me it has just stimulated a desire to go on and do the whole Milford trek. I probably did not quite consider who would pay this amount of money and take over 3 weeks off, and it is fair to say that all but one other person on the trip was retired, and as such I was considerably younger than everyone else. This was not particualrly a problem but some fellow travellers seemed to have major concerns about some of the accomodations and I have never been on an Exodus trip like this were people brought hard cases for luggage. Yes, there is camping, some of the huts are basic and there are drop toilets and shared sleeping platforms; however compared to similar in other parts of the world, these are relatively well appointed, clean and comfortable. You do need to be prepared to carry some group equpment, so you do need a 50L day sac, it's a bit unfair if those who do bring larger day sacs have to carry all the eqipment. We were extremely lucky with the weather, especially in the rain-ridden areas of South Island and I am sure at another time you will get considerably wet. You do need to be prepared for all climates, so pack accordingly with layers: it ranged from tropical beach in Abel Tasman to hiking in a hail storm in Mt Cook. The biting insects are worse than advertised, bring repellent and cover up. Gaiters are useful as the grass is wet in the morning and I found baselayer leggings possibly the most useftul piece of clothing, easy to carry, sleep in and wear under shorts to hike in, as the New Zealanders do. For th overnighters you do need enough clothing to change completely.
The instructions regarding baggage are clear but different people interpreted differently. You do need a 50 L sac for the overnight hikes, enough to carry sleeping bag, clothes and a share of the group equipment but you can leave your remaining equipment locked in the trailor. I brought a standard and comfortable rucksac with all my things as my main baggage and smaller 30 L day sac as hand luggage and for day walks and decanted out what I didn't need each time into a fold up travel holdall and walked with my riucksac. This worked well for me, others packed a ~ 50L pack inside their bigger main baggage and also brought a smaller day sac, this seemed like a lot of baggage.
As advertised this is a very fast paced trip, there is a lot of arriving late at accomodation and leaving early the next morning. Compared to other trips there is not a lot of time to rinse out and dry clothes, which might be worth considering when packing.
I took walking poles but strapped them to my pack on all but one day, the walking is not that difficult at all. However the climb is Lake Crucible is very steep and I found poles essential for both the ascent and descent. So I would recommend taking them.
Our trip coincided with the Christchurch earthquake (we were on the other side of the Alps at the time) and the later stages of the severe rains that hit that part of the world. This had minimal effect: the day in Christchurch and hotel were rearranged and we didn't hike into and camp at the Ballroom because of the height of the river but the alternatives were well organised.
If you like the outdoors and this will be your one trip to New Zealand and you don't mind some basic accomodation, this is definitely the trip for you. If you really want to experience the great hikes and love a hard walk, you may find this a bit disappointing and like me, find that it has just wetted your appetite for something more. Although badged as moderate-challenging, physically the trekking is not that tough, although some areas are very isolated and the volcanic scree is tiring. The climb to Lake Crucible and the Tongariro passage (when you have the heaviest pack) are the most difficult days, but really anyone that's used to walking regularly or is appropriately fit should manage these easily enough.