We had mixed weather on the Travers-Sabine and Routeburn treks, glorious weather on the Rees-Dart and Kepler but the Wangapeka was mostly wet.

Not to be missed - Rees-Dart Track, especially the side trip to the Cascade Saddle.

Update - since our visit, the route through the Dart Valley has changed.  In January 2014 a massive landslide blocked the valley and created a new lake.  A new diversion track has been created and the route was reopened later that month but check for the latest news before you set off.  More info and photos...
The Landslide Blog --- Dept. of Conservation --- Scoop

Don't bother - Wangapeka Track, unless you like looking at trees for day after day.  Having said that though, in a perverse sort of way I rather enjoyed it.  Wading through streams, swollen after thirty six hours of heavy rain, made it somewhat exciting.  As long as you keep warm there's something strangely satisfying about being so wet you just don't care any more.

Routeburn Track, unless you can organise the weather to suit your hut bookings and don't mind sharing the huts with a bunch of noisy morons who: -  are incapable of shutting doors behind them;  hold shouted conversations right across the hut;  do not understand the simple concept that if you spill food in the kitchen area you clean it up yourself;  can't grasp the fact that shining super-bright torch beams into peoples' eyes when they are trying to sleep is not a good way to win friends.

Unfortunately the Routeburn is probably listed in a '100 things to make you buy this book and make me rich before you die' type book, or something, so it seems to attract the imbeciles.  If I ever do it again I'll bivouac.