Hi Maggie!
I was lucky enough to spend 10 days on Star Dancer from Rabaul to Walindi in May. Fantastic!
Macro life if amazing (pigmy seahorse, mantis shrimps, mandarins etc), and you won't see more varieties of anemone fish anywhere else.
Don't forget the wide angle though as there are plenty of sharks and big fish to be seen as well. Buzzed by a fast moving bottlenose on one dive as well which was a real highlight!
Rabaul is actually a bit of a dump, although the volcanoes make up for this. Mind you I was told that the wrecks etc in the area are too laden with ash from the last erruption to make them worthwhile dives. Not sure I'd want to spend so long there, I assume Star Dancer would have stopped in the region if the diving was good, but we sailed straight round to the Fathers complex to the NW. I gather it used to be great, so be careful which guide books you read (ie get a recent edition!).
Walindi is beautiful, and the diving in the area is first rate. Its a little basic, but if it were luxurious it wouldn't be as unspoilt as it is.
Make sure you take a full suit of some form, as although the water is VERY warm there is some nasty stinging plankton in places that can be very uncomfortable. Maybe even gloves would be an idea!
Can't comment on Loloata really but have heard some good things.
Although as yet unfinished I have posted a few of my u/w photographic efforts on my web site if you are interested!
Any quetsions, let me know!
I know you'll have a great trip!