It isn't a question of need, it is a question providing useful functionality. Since it has a 'mouse over icon' display then why not have something useful displayed. Surely the whole point of the app is to be useful and user friendly - why force the user to have to click to open the app to read the temp and then have to click again to send it back to the tray when the info could easily be obtained by a quick mouse over icon, or better still, being permanently displayed in the tray instead of the icon.