I love writing on my phone. It's just a hand-me-down iPhone 5, but it has enabled me to have a whole writing life separate from my laptop and notebooks.
I primarily use Evernote for tracking pieces, but sometimes it feels easiest to use the Notes app that came with the phone. This morning, I re-wrote a whole scene from my current pilot into an email window. It's no-frills, but sometimes that's all I need.
The great thing is that I can squeeze in an interval of creativity anywhere. The expectations don't feel as high when you're just tapping on your phone. And I've found the time it takes to type out words is perfectly in rhythm with the pace of my brain, so I get in a nice groove, similar to when I write longhand.
Someday, when I get an iPad, I'm never going to want to get out of bed...