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Everything still fist, when I zoom in ("make bigger", >100%), but when I zoom out ("make smaller, <100%) a certain part is cut off on the right (and I can't "reach" the scrollbar in the Notepad pane or the close- and hibernate-on-hover-buttons in the Pages pane).
I'm now havong Sidewise 2012.11.23.0 and Chrome 23.0.1271.95 m on Windows 7.

I only have the "pages" pane and the "notepad" pane. I don't remember if this was standard or I manually removed the other ones.

That behaviour only appeared "once" (clicking the respective other pane's button repeatedly caused this to happen, but after this behaviour disappeared, it didn't appear again)

If there are plans on having an own process running for sidewise (in order to be able to hide sidewise from the windows taskbar) maybe that process could be used for inter-session-communication...