Hi Rea,
I'm fairly ambivalent about the use of pp. Having been trained as a trainer before they really took off, I'm not confident, but reckon I soon could be ( well, given my famous incompetence with things computer-related.....

). They're Ok, pretty much like OHPs are ok, but need and should be backed by sound knowledge as a grounder. So, I suppose I see them as simply a visual aid. You've had the handouts gone through, much as in any situation!
I once famously went on a course, recently, where the laptop stubbornly refused to cooperate, so the trainer (of the old school, who carried her old style stuff as back up) simply trundled out the OHP and got on with it the hard way!!
I do like the facility of spaces to make your own notes against the prepared handout, but that's counter balanced, I suppose, by the fact that the format makes redundant any note taking of consequence, so people who remember better by writing down may conceivably be placed at a disadvantage ..... I see I am appearing to sit on the fence, here!!
Overall I would say it's a tool that makes life easy for the trainer ( no writing of handouts etc) and it does mean learners can listen more without worrying about writing things down, but personally I find watching endless screens/slides etc rather disconcerting - I sometimes realise I'm planning dinner rather than concentrating

. Much like those early audio-visual French lessons where you spent hours in a stuffy, darkened classroom, half asleep and not really sure of what it was all about, anyway - or am I so old no one else can remember them?
Sue