I know this will sound crazy to a lot of people, but I’m really into using my iPhone for writing.
Now, this doesn’t mean I’ve developed some fancy method to use my fingers and thumbs with the virtual keyboard. For writing on my iPhone, I use Apple’s wireless Bluetooth keyboard — my favorite keyboard, ever (yes, it’ll also connect to my MacBook and my iPad). It took a while for Apple to allow you to connect a keyboard to an iPhone, and I love it. The keyboard’s just great, and iPhone screen’s got plenty of space to see your text. For years, I’ve been carting a laptop around, often because I want to have the ability to (a) do some writing, (b) handle email, or (c) take interview notes. But now? Well, I don’t need the laptop, because I can do all of that with my iPhone and a Bluetooth keyboard.
As for apps for writing, that depends on the task — right now I’m typing directly into the iPhone’s WordPress app (this website runs on WordPress) — but I also like the SimpleNote app for notes and general writing. That said, if anyone’s got tips on writing apps for the iPhone, I’d love to know about them.
ALLAN HOFFMAN 
I bought a stylus a few weeks ago so I could write on my iPhone. Didn’t realize the Bluetooth keyboard was available. Allan, thank you so much for a terrific tip.
I have a stylus too, mainly for editing photos or a bit of sketching, but the keyboard is what I use the most. I used to carry around my MacBook more often, but now I usually just take my iPhone and the keyboard.