Type in your equations/math, hit render, drag the PDF (or many other image formats) to your slide.
LaTeXiT gives you the best of both worlds; wonderful rendering of math, with the bonus of using Keynote (which is the best presentation software on any platform in my experience).
That looks nice; part of the advantage of beamer, though, is that the equations and (especially) inline variables are automatically positioned correctly and consistently -- it looks like that might not be the case for LaTeXiT.
Type in your equations/math, hit render, drag the PDF (or many other image formats) to your slide.
LaTeXiT gives you the best of both worlds; wonderful rendering of math, with the bonus of using Keynote (which is the best presentation software on any platform in my experience).
[0] http://www.chachatelier.fr/latexit/