When I'm using the system monitor and I change the window size (or maximize the window), the next time I launch system monitor it appears at the same size (which is almost good).

But if the window was maximized, it appears as an unmaximized window that takes almost the whole screen.

system-monitor should behave like this:
1. If the window is maximized store a "window is maximized" setting
2. If it is not, store the current window size in a "window size" property

When restoring the window, set the default size to the last saved size and then maximize if necessary. This way we'll get exactly the behavior that users (at least I) would expect: a maximized application reappears maximized and unmaximizing the window leaves it at the size that it had before it was maximized the last time.

I'll cook up a patch for this.