Thunderbird's distance learning programs use Tegrity recordings extensively in all our courses. We generally recommend short (less than 20 minute clips) for each week of classes. Classes generally have 1-4 Tegrity session per week. Most are pre-recorded, and include an overview of the week's assignments, topics, and lecture content. We also have 'technical' sessions for some classes to show the steps for working through a problem, or developing a spreadsheet.
Finally, many professors do a 'spontaneous' Tegrity session to wrap up the week's events, and provide feedback to the students on their case discussions. These recordings are done from wherever the professor is located, and sometimes include airport terminals, or vacation spots with family. I think they add a lot to the personal connection between faculty and students.
Recently, we've also added the feature to allow students to record online presentations for their classes.
Tegrity is holding a number of webinars on incorporating the technology into distance courses. You can sign up here.