The thing I've really learnt - and have been a bit surprised by - is how quickly the novelty of all the 'cool' apps wore off and how much I'm missing the simplicity and rock-solid functionality of my old Palm phone. None of the new phones comes even close for basics like calendar/contacts/notes etc...
The novelty does wear off but I've gotten used to several iPhone apps which are at core pretty damned good.
Palm pretty much _defined_ the mobile calendar app IMO and I've never seen anything as good on any platform; in fact, the old Palm calendar is better than lots of desktops. Certainly the iPhone's calendar doesn't come near it. Lucky I don't use my calendar all that much, but it pisses me off every time I have to.
Notes and stuff were never that great on the Palm and there are some much more advanced apps on new platforms, though strangely not ones I've found very compelling (Evernote, for instance, just leaves me cold, no matter how much people rave about it).
Tasks... the Palm's to-do system was also good, but a bit limited once you got past the immediate unless augmented with something like Agendus, and I think there are some good task apps out there, particularly the really hardcore stuff like Omnifocus. There are also now web task apps with mobile interfaces which compete well, though obviously you need net access to use them. I use Things, which really does do the business - I find it balances complexity vs ease of use very well, particularly being able to easily flag things as "today" wherever they are.
Contacts on the iPhone, I can't complain about, nothing special but it's all tied into the OS so every app can use the data easily. You want contacts to be unobtrusive really and just have their information available everywhere, so that's fine. There's only so much you can do with a contact list.
