I typically have used either Beamer (what I currently use) or Prosper (what I used to use) document classes in LaTeX for my slides and have since probably the 90s. For me, the big thing with using LaTeX is that I can get consistent fonts between the equations on my slides and the symbols in my figures since I draw my figures using LaTeX in some way (usually TikZ or Sketch[0]). Plus, I can have my figures under source control in a manner that supports simple diffs.
[0] http://sketch4latex.sourceforge.net/
Note that Sourceforge was down when I checked, but this should be the right URL.