I very often miss incoming IMs in GNOME 3 when not really using the computer.

For example when I am doing some other work at the desk or watching tv with the laptop next to me. IMs just pop up for a very short time and if you don't always have an eye on the screen you don't noticed the message. This was not an issue in GNOME 2, where incoming IMs were always visible in the tray.

It would be important if the message queue would be shown after the message preview disappears if there is no mouse/keyboard usage at that point. If the user returns to the computer he now has a chance to notice the queued messages. However, the message tray could be hidden after a few seconds of mouse/keyboard usage.