SWMBO and I toured around New Zealand in 2001, along with my 3mp Nikon 990 Coolpix digital camera. We got tons of great photos, and had a total blast.

Things of note: work out how to store the gigabytes to be accumulated while you're still on the road.

Photographing in rainforests is difficult -- very low light levels require high-ISO and/or a tripod. A monopod at the very least. And the camera has to be able to focus in low-light.

It was very, very wet while we were there. The convenience of being able to keep the camera inside my raincoat when not actively snapping a photo was invaluable. An umbrella could also be useful.

A huge expensive and bulky DSLR is not necessary.

Having said that, we more recently just got back from bouncing around Australia. We took the Coolpix again, but also my Canon DSLR (20D) and some relatively light (but good) lenses. Shooting in the rain forests was a breeze, as was capturing dozens of the small birds and animals lurking therein -- not possible with the Coolpix.

Again, tons of good photos to sift through, and the big expensive bulky DSLR was a lot of fun to use there.

Go figure.

If you have (and want to reuse) some good Pentax lenses, then maybe consider the Pentax *ist-D DSLR. Otherwise, the Canon 20D w/17-85-IS lens, or the Nikon D70 with kit lens. Hard to go wrong either way.

Cheers