This was our second cruise, but first P&O. We can't really fault P&O, the main problems we had were with our fellow passengers. We are a married couple in their late 20's from Sydney.
Pros: Our cabin steward (Ronaldo) was fantastic. La Luna was outstanding. Food at Plantation buffet was surprisingly good. Food at Waterfront was consistently good. Lifou and Pentecost Island were amazing. Large range of organised activities meant you could do as much or as little as you wanted. We did trivia each day and went to a Martini Master class.
Cons: Drinks service at Waterfront was very poor. Production shows were awful. Bars were too small and not enough of them (very hard to get a seat at Connexions in the evenings). Comedians weren't very good. Our cabin smelled like cigarette smoke for the first 2 days. Our cabin was under the theatre and the stage seemed to be used constantly for rehearsals - sounded like a herd of elephants were jogging on the spot. My husband got sick from the steak at Salt Grill.
But the worst thing about the cruise were the other passengers. We did meet some lovely people at dinner each night, but en masse it was a nightmare. Rude, mannerless people constantly cutting in line at the buffet, heckling the musicians, smoking constantly, complaining about everything, kids in the adult pool. And stupid too - we saw one man waving his glass under the hand sanitiser unit trying to get water out of it (and this was half way through the cruise) and another lady using her hand to push the lever on the water dispenser rather than her glass.
If we cruise P&O again perhaps a New Zealand or Tasmania cruise would have a more sophisticated crowd.