Looks cool - a bit like Infinote (which I have, but don't use incredibly often) but with a cuter design. Since it's free, I'll get it.
I doubt I'd stick with something like that, though. I want to write notes, scribble things, underline things, draw circles and lines around stuff, etc.. not type. So a sketching type app always works better for me.
You can sketch inside of a Popplet. I don't think of this as an app so much as an organizer. If I were Apple, I'd acquire this and let Files from various apps populate a Popplet, with the App "zooming" to view or edit each file.
Something like that would pretty much be the full equivalent of Courier.
Try using Popplet as a mind mapper. This has the potential to subsume the entire functionality portrayed in the Microsoft Courier ad.