We booked the January cruise from Sydney to New Zealand on the Diamond Princess, seeking 12 days of relaxation and just enjoying the ocean. This is exactly what we did.
Rather backwards, but after booking the cruise we read a number of reviews on the ship, most describing experiences during the Alaskan cruises, that weren't necessarily glowing, this made us a bit nervous given a terrible P & O cruise some years back.
Although the ship was full, we experienced very little in the way of line ups, check in at Sydney was amazingly efficient and courteous. If peak times in the Horizon food court were avoided - there were limited line-ups and great views. Getting on and off the ship at ports was easy. There was always somewhere to get away on your own, without the crowds.
Cabin and balcony, rather small but generally comfortable and well appointed, with good storage. Pillows were lousy though, even replacements were awful! A more broad no smoking policy would have been good, as when surrounded by a number of smokers, the balcony can be uncomfortable. The location of the cabin was excellent - Baja Deck, aft of midship.