I've tired of carrying around my Palm Pilot in addition to my iPhone/iPad because I haven't found anything to replace the Palm Notes application. I looking for a simple database or notes program that meets the following criteria:

Categories: Each item can be a member of several categories, but I need to be able to view just a single category at any given time with only it's members shown (just show me category 'A').

Search: I need to be able to do a search through the DB and have it list all occurrences of the search term. Need to be able to search not just the title but the entire note for particular words (find all notes with 'web hosting' in title or text).

Password protect some items: This is not mandatory, but it would be nice to have a category called personal where I stored my bank account numbers, CC info, etc and password protect it.

Sync/Edit on PC: I expect to enter most of the data on my computer (PC not Mac). The iPad app itself could almost be read only. I also reference the data on the computer often so I need a similar program on the computer for reading/searching (eg an Excel spreadsheet wont cut it).

If I end up putting sensitive (PW protected) info in it I'm not even sure I want "cloud syncing", maybe just a local sync of some sort or even one way copy from PC to IOS.

Thanks for your help

Evernote seems to fit your needs. It is a mature product and has native versions on many platforms, including iPad and PC.