Using slides to present maths is horrible in our opinion. Somehow we cannot form a mental picture of what the speaker is talking about. We do not know a precise reason. There are some annoying points of slides. Sometimes the speaker goes on to the next slide before we finish reading the current one. This can be mitigated if the speaker pauses somewhat before turning the page or if we request the speaker to hold still. Yeah, we did this in a talk we were really interested in and pissed off everybody else. When we need to refer to something the speaker has talked about, we cannot go back to the slides. A single slide can only contain that much information. To mitigate this, we take notes. Unfortunately the room is usually quite dark for taking notes... and darkness is sleep-inducing. Coupled with our slow IO speed, it always goes badly. (Slow to read stuff on a slide, slow to take notes. Also slow to convert words into mental picture. Sorry. We are fast in only one respect: Once stuff is placed in the mental picture and connected to other stuff there, we are super fast. BTW the process of forming mental picture happens async to taking notes. Why do we work without pause? To avoid the costly and tedious process of forming mental picture.)
We are not sure if slides work for other disciplines. Probably maths are the densest discipline. One slide cannot contain even a fraction of an idea. Too make slides work probably we need space to show 6 slides simultaneously. The screen showing the slides should be legible in bright indoor condition.
BTW we have noticed the trend of having a website in the form of slides to present the product. Anyway the readily conveyable things are generally superficial. The depth is never easy to see through.
[Update: There is another point with slides.
When we present by writing on the board, we will compress the data because writing is a costly operation. We leave out the extraneous stuff and convey the gist. This is what presentation is about. Convey the idea and people can dig into the details and subtleties later. When people use slides, they give a more formal statement laden with the non-essential. The extra stuff is unhelpful and distracting. Also some people are not skilled enough for making slides. All they know is to put in words. Sometimes a suitable diagram conveys idea much better. However figuring out what to put in a diagram and making the diagram are much harder than typing in words.]