I just purchased Pocket Informant HD and have to agree that it's a excellent product. I find entering appointments, tasks or projects a breeze. Just tap on the day and enter the details. What could be simpler? Yes - you could say it's complex (as I did earlier) but that complexity is also flexibility in that you can configure almost any way you want to.
For example, the iPad version has changed the 'Day' view of the iPhone (which displayed a day at a time) to a 'Days' view that displays 'days' - but a week at a time to 'take advantage' of the iPad's bigger screen. To begin with I was disappointed; I like to go through my diary a day at a time and this new view - effectively a week at a time - seemed to preclude this. But, almost accidentally (and I can't see it explicitly documented anywhere) I discovered that, if you use the iPad's 'pinch' gesture you can expand the 'Days' view to show as few or as many days at a time as you want. So now I can 'flick' through my appointments just as I wanted. In fact, I read in one of the reviews in a well-known periodical that one of the 'joys' of Pocket Informant is discovering all the undocumented features.
To me, one of the other big advantages of Pocket Informant is that it (optionally) imports all the appointments from the iPad's native calendar app. This not only means that if, like me, you've been using the native app since you first bought the iPad, you don't have to enter all those appointments again, but it also means that other apps that use the native app to display incoming appointments or tasks (like the iPad mail app, for example) will immediately show up in Pocket Informant. These 'imported' appointments are highlighted in Pocket Informant too, so that you can distinguish them from Pocket Informant's appointments.
If you have iOS 4.2 then Pocket Informant also gives you a very wide choice of alarms and pop-up reminders and, if it's running in the background, these are active even if you're not using the app (of course - wouldn't be much use otherwise!).
All the iPad's gestures are supported - so you can 'flick' through pages of your diary (like many people wish they could do with the iPad's native calendar app), scroll up and down, pinch and zoom etc etc.
In the short time I've used the app, I've become a convert and don't resent paying (for an app, at least) a relatively high price for a very well designed and implemented app. I haven't experienced any of the 'instability' problems reported by some users in the app's iPad store reviews.
And - of course - I should say that I have no relationship with this company whatsoever.
Tim
Scotland