Spark could use some sort of limiter to ensure that the contact list and chat windows stay fully within the bounds of the available screen area.
I run windows with my task bar at the top of the screen and many times, upon logging in, the top of the contact frame will be under the task bar, making it inconvenient to change the window location (have to unlock the task bar, which forces the contact list back within bounds; place window; re-lock taskbar).
Additionally, during the course of several conversations, the chat window will creep up the screen until the title portion of the window is off-screen. At this point, there is no known way to grab the title bar (unlocking the taskbar doesn’t work on that, unless there is a taskbar on that screen).