That is what I came up with too, just based on a quick look at the TerraTooltipSkin code.
Although it sets up a mouse listener on the Display, I don't think of that as being a problem.
You may well be right about there being a better way to achieve this though.
The only issues I saw were
- Configuring the Display used for the tooltip so that it doesn't accept focus.
That way, the primary Pivot window will continue to have focus.
- Disabling the fade transition (but I never have them enabled anyway!)
Screenshot attached if you are interested.