there's no window that pops up to tell you it's going to exit -- the only indicator (on windows atleast) is the limewire icon in the system tray. do macs have any sort of process viewer that lets you see what is currently running? try doing the shutdown after transfers while something is transfering and look at the process viewer -- if you see 'java' (or limewire, not sure what the macs will display), then you can know it's still running.

someone who uses a mac would probably be able to answer this better than i.