Michael Gartenberg and Chris Sells blame the user, not the tool. Room enough for both, I think. There is always the question of doing the wrong thing more efficiently. Or using a tool as a crutch or substitute for presentation prep and delivery skills.

I'm quite fond of some common tips:

1. One idea per slide
2. Replace words with pictures
3. Fewer words are better. One word or phrase is best.  
4. Talk over slide transitions

That said, nothing replaces rehearsal to perfection, clear organization, ruthless editing, and people skills.