I was just playing with the scrolling in Project Macaw (Twitter client) when I realised that the UI is much smoother in landscape orientation with the speakers facing downward.
It's most noticeable with Mojo FPS Booster and Mojo Smooth Scrolling installed, in landscape with speakers downward the UI is smooth and consistently hits 60fps. If rotated into portrait or turned upside-down, the performance drops considerably and scrolling becomes very choppy.
I'm unsure if this is a Mojo-only phenomenon or if it applies os-wide. I suspect it's something to do with graphics drivers, most likely vsync. Most curious, and badly in need of a fix.