TBH there is not any more faff than P&O, their app and The Princess Medallion do almost the same things, and you can totally ignore them for MDR dining if you so wish, and Alfredos new pricing puts it on a similar footing to the Glass House and Beach House. As regards the Princess Plus, then IMO unless there is a 50% reduction offer then it's probably not worth taking, and Princess do at least have regular offers on Princess plus, which of course never happens on P&O.
Otherwise the Princess experience is very similar to P&O, but a bit more upmarket, with more and better musical groups, and lots of entertainment taking place in the Atrium, instead of it being a wasted space as on Britannia, Oh and much superior customer service.