Hackpad was cofounded by one the original authors of Tomboy, which was a really excellent desktop note taking app that has withered since. It was based on a fork of Etherpad, which was a startup that made a multiplayer, web based note application- that company was purchased by Google, the code open sourced, and the service wound down. Sort of a long sad trip.

I really liked Tomboy, I enjoyed Hackpad, although I quit using it over time- I collaborate much less now.

I don't take notes anymore, with software or on paper.