Typically, "tip of the day" feature is not really loved. Often, the dialog for showing the tip blocks the main view of the application. Worse, this dialog is even modal, you have to click it to make it disappear.
For SpeedCrunch upcoming version 0.8, I play around with the idea of showing a short tip as a yellowish widget inside the main window. It will disappear automatically after couple of seconds (even with some smooth translucent and animation effect). I'm still thinking whether the tip should be displayed at start up, or only from a menu item.
I hope this kind of tip is non-intrusive and yet allows the users to learn a thing or two about SpeedCrunch features.
So, what do you think?
(Yes, I know there is typo in the screenshot :-)