We (DM, DH and I, two iPhones and an android) use Cozi Gold. My mum has always used a date book but after a few health crises it was useful to know what doctor appointments were planned or had taken place and we agreed to try an app.
My mum loves her iPhone and uses it with ease but there's so much button pushing to get a simple entry in the diary, I'm hoping there's something easier to use out and about? Like if it was visually similar to a date book, and you could just touch the date and time and type a brief description. Not sure if I'm describing that well. Cozi entries seem time consuming, setting date, time and reminders all separately as well as entering text, it's too much when standing at the reception desk.
There's also no private area so you can't use it for things like Christmas gift lists. It'd be nice to be able to share what you want to share and not have absolutely everything visible to everyone.