I find it useful as a massive canvas for keeping a bunch of stuff in context, visually. And accessible via Mac and iPhone. But it is sorely lacking a major feature: highlight text to add a hyperlink. I end up with full URLs instead of hyperlinked words and it's pretty messy.

I use it regularly to do rough sketches of objects on my iPad to model in CAD later on the computer. It doesn't feel right for artwork or notes or basically anything else.