A rather good article posted on presentationzen this week talked about new research from the University of NSW on "Cognitive Load Theory" which more or less says it's hard to read and listen at the same time. Some slightly lazy journalism resulted in leaping from that to the sensationalist "PowerPoint is dead" type headlines.
The point (sic) is though that rubbish slides with loads of words and boring bullets are hard to read while someone is talking at the same time. dur yeah.. so crap slides don't help your audience understand you? Goodness I'm amazed! Better to think harder about what you are going to say and use more graphical ways to reinforce and enhance your delivery.
Sweller himself says:
"It is effective to speak to a diagram, because it presents information in a different form. But it is not effective to speak the same words that are written, because it is putting too much load on the mind and decreases your ability to understand what is being presented."
This is of course why PowerPoint 2007 (and Word and Excel) has the concept of Smart Art where with a couple of clicks you can turn your boring bullets into a diagram - and a pretty one at that. We are on the same side here - use the tool to help you not hinder you. If you have a power drill, it helps to put the drill bit in the right way round.