Ask HN: Success with “tip of the day” in engaging users?

My company's ed tech product has an array of powerful functionality that is chronically underutilized. I work in implementation support, and IMHO our documentation and training are extensive and user-friendly. However, I am interested in product tweaks that could help engage users (who underutilize core functionality then fail to obtain desired results) in getting more out of the product.

Specifically, have you had or do you know of experiences implementing a "tip of the day" pop-up or display? I have always thought this was a powerful part of videogames, such as teaching a spin move in Madden.