Mmm, it's great. Only one minor hiccup though, switching from the main page to the sketch area resets rotation. You're in portrait and selecting a sketch (or vice versa) returns you to landscape and you have to turn the N900 around all over again. Fix that and you have my vote for extras admission, though I know rotation implementation in PR1.2 is still sorta buggy. Maybe the Pen Pen sketch area can read the rotation status of the main window when it is launched and set it's own rotation accordingly - or something.
I also vote yes for lines and boxes (and also remembering settings for them for every new sketch). I usually use it as a note taking app, and the lightweight size, speed and simplicity of Pen Pen has already made me ditch Xournal. With sort options (by date/name or even priority) it would be a killer note taking app, though I'm aware its meant to be a sketch app.