Not being able to see the bottom third on the e-ink side is a bit annoying. For writing notes in class I just used the top two-thirds. I could see on the projection when I was running out of room. Using text I've marked up, I actually did the export to pdf and opened it on the tablet side. This way the students could see the colors, instead of just gray scale and there were no issues with not being able to see part of the document.

I don't mind the tape recorder. I often record myself so I can improve my explanations of certain topics. I also record class discussions so I can remember comments or items that students bring up without trying to take notes as we talk. I also record student presentations so they can hear themselves and improve their presentation skills. (I'm looking forward to using the video camera for this in the spring.) I always let the students know if I am recording. As for myself, I learned quickly to assume everything I say and do in class is public record. That's not to say that I don't have academic freedom, but I am very conscious of making all sides of a controversy known, when something is my opinion, making it clear that I'm making a joke, etc. I'm also untenured, so I often have people observing my classes. I'm sure there are others that will disagree but I don't think you have any reasonable expectation of privacy as a teacher in a classroom.