In the good old days when I taught the first course in the core graduate microeconomics class, I would lecture at the blackboard, without notes, and derive every equation and graph from first principles. The same exact stuff would be in the textbook, but my talking through it presumably added value for the students beyond what they got from reading the book. In intermediate microeconomics, an undergraduate course, I would do something similar part of the time. I had much less a sense of the value add for the students, but it was the method of the discipline and I felt obligated to work the students through the stuff in a thorough manner. Among certain colleagues, both in the department and elsewhere on campus, I developed a modest reputation as someone who taught the right sort of intermediate microeconomics course - with an appropriate balance of math and intuition in the presentation. Other instructors would use more calculus, do less graphically, and be less intuitive. They'd also cover somewhat different subject matter.
I stopped doing the graduate course in 1993, 1994 or thereabouts. I continued to teach the intermediate course till 2001, though as part of my SCALE project the class moved to large lecture (180 students where normal sections had 60 students). When I realized students in the back of the room could not see what I was writing on the board, I switched to PowerPoint - perhaps in 1998 or 1999. It was pedagogically a step down because it showed the results as finished product, like the textbook, rather than actively constructed in front of the students. But at least the students could see what was on the screen.
When Tablet PCs came out I experimented with them for doing the lecture and making movies of that, but at the time I wasn't teaching these courses. So it was more a skill to acquire so I could pass it on to others who might be interested than it was an investment in my own teaching. More recently I have been doing some teaching but I thought doing the math in Excel more innovative than the old fashioned way and I invested in that. But the results have been mixed at best. So I've decided to supplement the Excel with the old fashioned way, but done on the iPad. I will then make exercises for the students to work, some online ahead of class and others during the live class session. I hope I can improve student understanding of the math models this way.
I'm just getting started with this. Here is the first set of lecture notes I've done on the iPad. My plan is to write them out this way first, then make a screen movie where I write them again. And then do yet one more capture where I put in my voice over. I've made enough screen movies before where I've learned there is a certain feeling of pressure while recording. You want to think in a continuous flow as in the live class setting and feel you'll ruin the movie if that doesn't happen. So I hope copying the lecture notes while the movie is being made will be a way to get a better result since copying is less cognitively demanding. We'll see. This content gives an algebraic/calculus look at material. I have other content that covers this graphically in Excel (this YouTube movie, this Excel file, and this YouTube movie which has the demonstration of the result starting at the 4:14 mark).
I also want to note a certain feeling of joy from making this. It is pure nostalgia for the way I lectured back in the early 1990s. It is not based at all on whether students will get value from it, which should be the primary determinant of whether to do this sort of thing. It is only that I did this so often in the past that I feel I'm hard wired to do it, even now. My handwriting is certainly no great shakes. But I think the product is readable.