Number seven in our list of most popular Trainer's Tips, and it's a second top 10 entry for Andrew Bradbury. Here he offers advice on the best method of delivering training to be sure that the learning sticks.
Here are some average figures which might be useful:
People will remember about 70% of a purely verbal presentation, three hours later; but as little as 10% after three days.
People will remember about 75% of a purely visual presentation, three hours later; and around 20% after three days.
People will remember about 85% of a mixed verbal/visual presentation three hours later; and as much as 66% after three days.
Making the presentation interactive is reckoned to support an even higher rate of retention.
These figures are from a book I wrote a little over 10 years ago, and I know they came from a reliable source - I just can't remember what it was!
As to "death by PowerPoint", I suspect that nowadays (given a constant programme of improvement) that is more of a commentary on the lack of creativity of some of the people using PowerPoint than an accurate reflection of what the software can do in the right hands.
You might want to look at this book which explains various ways of creating PowerPoint presentations that capture the audience's interest rather than just bombarding them with bullet points: Killer Presentations by Nicholas B. Oulton, How To Books (2005).
Anecdotally, over 25 years as a sixth form tutor, training course designer and trainer in the IT sector, all using mixed media, indicates that this approach improves learning for a majority of students/adult learners.