Hy,
On Ubuntu 12.04 LTS with the latest Firefox (29.0) if anything is shown on the sidebar, when it’s open, you can’t zoom with the mouse wheel since the sidebar div can’t lose the focus even if you click on the canvas.
This isn’t an issue in Chrome on the same system.
This is a little thing, but I thought I will let you know, because it’s a little inconvenient.