The mobile design does leave a lot to be desired. It does fit my needs however because usually I am just jotting down a quick idea or reference for later. I can see how switching between multiple notes quickly can be difficult.
Not related to the parent comment but I have been using the math plugin and I love it. It does unit conversion and lots of other things!
Is it just me or is Rails really complex? Its abstractions are so far removed from anything familiar (HTTP, SQL) that its difficult to understand what is happening unless you deeply understand the framework.