I have not been that happy with the Notes application on the iPhone. Text entry is a pain on the iPhone, especially with larger notes. Ideally, for some notes, I would want to type them on my computer and have them synchronized to the iPhone, but Apple doesn't currently synchronize notes on or off the iPhone.
It looks like Evernote might do exactly what I want. I can create/edit notes on any computer on the Evernote website. Then on the iPhone, I will use the application. This will make it very easy to access these notes. And, it is just as easy to create notes when I am out somewhere, if I need to.
Evernote has some other features that are pretty cool, but I am not sure if I will use them much. You can upload a photo, and Evernote will use OCR on it to allow you to search for words in the picture.