I use a hybrid version for some of my classes which take place in a room that allows this: I use computer slides (and animations, computations, etc.) and the board. I learned this from my colleague Serkan Hosten, and it works really well in some classes. E.g., I use slides for definitions and theorems (including the relevant ones from the previous lecture) but then work out examples and proofs on the board. This has the obvious advantage of spending time on exactly the items that need time and just the right pauses to get digested, but it also has nice side effects: e.g., the statement of the theorem will stay on the screen even if I'll have to clean the board.