I switched from sidenote. I kept accidentally triggering sidenote by moving my mouse to its edge of the screen, and I'd frequently find that either (1) I was typing in sidenote when I hadn't meant to be, or (2) I was trying to type in/copy from sidenote and it had somehow lost focus. Scribblet has a nice configurable global hotkey, and it's an actual window that doesn't slide in and out, so when you're typing in it, it doesn't try to disappear, but it is easily dismissed with the common cmd-W shortcut when you're done with it. I could do with bolding, but I'm quite content without.