This doesn't affect the functioning of the plugin but it's slightly annoying for admins like me who are obsessed with the server logs...
Whenever a player disconnects it causes the following log to appear twice. This is definitely caused by GUIAnnouncements, I've tested it with the default config and it still happens:
*.*.*.*:43256/76561############/JimDeadlock disconnecting: closing
*.*.*.*:43256/76561############/JimDeadlock SendMessage failed: InvalidParam
*.*.*.*:43256/76561############/JimDeadlock SendMessage failed: InvalidParam