[danielford]

Not an option. Moving my teaching materials to other programs would be a mountain of work at this point, but in five years it will be exponentially worse.

PowerPoint is the main issue. I've made a lot of animations for my courses that I'll have to remake from scratch if I switch programs.

[Jare]

If you accept that you will be switching at some point in the future, the sooner you start migrating to an open optionlike LibreOffice, the better. It feels good to know that nobody is going to pull the rug from under your feet.

(that said, I don't love LibreOffice and I don't know of any truly solid presentation solutions that are open, cheap, multiplatform and reasonably future-proof. I'm a coder so I've ended up in HTML5 + Sublime Text for my slides, but tooling for this option is rather limited)

[darkestkhan]

LaTeX Beamer is very good for presentations.

[axiak]

For new stuff, prezi is an awesome platform for teaching presentations: http://prezi.com/2hk390sfkqjh/the-astronomy-masterclass/