A Little Help for My Treo-Loving Wife

I’m looking for some suggestions from one of our loyal readers (who is also happens to be a former Treo user).

Here’s the situation . . .

My wife used the Treo for many years and loved it. Not a big fan of adding additional programs to her handheld, she used the applications that came on the device.  An incredibly organized individual, she used both her Palm device and the desktop program to house tremendous amounts of information (everything from directions to reminders and account information).  I often teased her that her lists had lists. 

The way she structured things over the years worked exceptionally well for her.  For example, she had nested categories within her memos function: “Birthdays”- under which would be “August”, with a list of individuals whose birthdays occurred in that month and the specific date next to each name.  Another example: “Miscellaneous”- under which would be “House”, with a list of items to purchase, organized under bold-faced names of the stores in which she needed to purchase those items. 

Now that she’s made the transition (FINALLY) to the iPhone, I’m not sure which application/s to recommend for her.  Obviously, I’m familiar with the notes and memo apps available to her through the app store.  However, never having used a Treo myself, I am uncertain as to which ones would best replicate her past experience.  So . . . I’d like some advice from you.  What memo apps (and/or other Treo-type functions) work best on your i-device?