Interesting, I haven’t tried mouse on iPad yet myself. I do wonder how much people actually use mouse on iPad now.
I haven’t used much of scribble either. But I could see how it might interfere with navigation, especially when there are large text fields like posting in forums. Styluses are most efficient when used with keyboard shortcuts (hold space bar to pan/scroll). It’s definitely trickier with no keyboard.
I really hated my iPad experience with a Bluetooth mouse. I ended up getting a Magic Trackpad 2 and love it much more..but its an expensive way to get mouse support. It's mostly the scrolling and not liking how the extra buttons can't function as a "back button" in things like Safari with my Logitech Bluetooth mouse. I like using gestures on the Magic Trackpad. Granted for years I've always used the 4 and 5 finger gestures on the iPad.
I find using the pencil for normal iPad really awkward for me. In the short time I played with it, switching between handwriting mode and needing to enter things like space and normal navigation not really smooth as expected (the way I think about using it). I didn't like the location where you scribble depending on the apps I tried, the writing location can be in a really awkward spot. But I haven't played with this in a while scribbles was introduced so maybe there's a lot of improvements?