When steam was in beta, clicking X on the window would actually close it. The client would continue to run, and the way to bring the window back up was to click on the tray icon. This is very similar to how Skype, Xchat, Dropbox, etc work.

Some long time ago, this was changed so that clicking X on the steam client would minimize it, and then further trying to close that minimized window would exit steam. This kind of defeated the purpose of the system tray icon, as clicking on the minimized task bar window would open steam back up.

Please, bring back the system tray icon only mode (at least an option for it). Not having more clutter in my taskbar is a good thing, especially if i want to have steam running for updates or chat.