That's a moneymaker, for one thing. For another, they're the industry standard, and yeah the formats are proprietary but if you take a couple years break and start paying again, your files are going to open.

I was thinking more of products like Roam Research. Not to pick on them in particular, I know a lot of people like it, but it's just a non-starter for me.

The Moleskin iPad app is the one I'd most like to use, if they came up with a different business plan for it.