I agree with most of the previous reviews regarding the 2 night 'taster' cruise from Southampton before the ship's official inaugural cruise. However I do think many of the issues are just teething problems in a new ship which you would assume a respected cruise line such as Princess will iron out. I can empathise with the irritation when you have paid for what was quite an expensive cruise (except of course all those travel agents on a freebie!) So problems with check in, slow restaurant service, haphazard entertainment organisation, etc should not really put you off. I'm confident they will be fixed.
So I'll concentrate on hopefully the 'permanent' features of this new ship. First off, I really enjoyed it. The atrium has the 'wow' factor. The Horizon Court is very large with lots of tables and a huge amount of choice. The Allegro restaurant looks very smart and the waiting staff were friendly and efficient. We also ate in Sabatini's which was superb. Again the waiters were first rate and the food was excellent. We enjoyed the fountain 'show', the 'Sea Walk' and many of the bars. The ice cream parlour was good and the various shops were okay. The outside jumbo screen was very impressive.
I liked the theatre and the show ('Colours of the World' or something similar) was absolutely fantastic (and I don't usually enjoy those type of shows). We also saw other acts around the ships which were very entertaining.
The cabin was smart and reasonably well designed without being spectacular. The ship as a whole is decorated very subtly. So none of the garish neon colours you get on some ships. Also the 'theme' bars and restaurants were not that 'themed'. For example, there was an 'English pub' but I walked past it several times without realising that was what it was supposed to be. Each bar looked very similar irrespective of whether it was a wine bar, bellini bar, etc. I don't have any issue with this one way or the other but I note several reviews have commented on the 'beige-ness' of the ship.
The staff everywhere were very good. Everyone was friendly and efficient. I never had to wait for a drink or to get served.
The kids clubs were very smart (perhaps a little too conservative). The teenagers club looked excellent with a New York loft design and its own outside sunbathing and hot tub area (made me wish I was 16 again!).
I would definitely consider booking a longer cruise on the Royal Princess. It's a lovely ship which is well designed.