Hiding the userlist (by deselecting the tickbox) affects what joins/parts are shown. More specifically, only parts are shown. Tested using 1.5.0-1040 and PtokaX.
I know there are protocol-related reasons for this, but it's counterintuitive that hiding a cosmetic feature should have this effect.
There's some sort of overflow in the system tray tooltip, causing the uptime to not be displayed correctly.
Or, at least, the problem existed when i took this screenshot.