Simplenote is one of my favorite services for iOS and Mac. I make every small notices with it (for bigger I use Evernote).
For using Simplenote on Mac you car try nvALT.
These are the kind of services I want to use on my iPhone. Fast, simple, reliable.
And now is Simplenote with the version 3.2 ever faster on iOS. Yes, I saw how fast it is.