TLDR: Beautiful modern ship. Expensive. Below average food quality. Restaurant service is bordering on rude. Constant cash-grab. No adult-only pools/hot-tubs. 'The Retreat' is a rip-off. The 'My Holiday' app is hopeless but necessary to book everything.
The Iona is a beautiful. modern cruise ship. The staterooms are bright and airy - perhaps a little smaller than other P&O ship according to fellow passengers - but comparable to other new cruise line ships. There are cabin issues well documented: the Promenade rooms are terribly overlooked and the front cabins - as with deck 5 balconies - have storm doors that effectively turn them into Oceanview rooms when the weather is bad. Cabins are very noisy - patio door/frame creaking was a common complaint from nearly all balcony passengers I spoke to.
Cabin cleanliness is debatable. Further details on this below but sufficed to say it is a lot worse than other cruise lines.
11737 - Starboard facing single balcony cabin. Perfectly fine for a solo traveller and lovely to have your own balcony.
Oddly, all cabins on Iona are only cleaned once per day, in the morning between roughly 8am-2pm. There is no turndown service and no special treats in your cabin (no chocolates or towel animals). If you make a mess, you have to wait until the morning. Bedding was changed one during a 2 week cruise and carpets vacuumed very infrequently. Bathrooms were cleaned well but the cabin mirror and balcony door was not cleaned and the smears I notice on day 1 were still there on departure. Overall, the standard was well below par in comparison to the alternative cruise lines.