In addition to showing how to make the most of pulling a rabbit out of a hat, Jobs also demonstrated how (and how not) to time the changing of slides with what you're saying.
1. Sooner rather than later
One very common habit in this slide-dependent age is that speakers can't wait to press the button to bring up a new slide or a new bullet point. This creates the impression that they don't know what to say until the prompt has appeared on screen to remind them. It also gives the game away to the audience before you've had chance to deliver the news to the audience from the horse's mouth (i.e. yours).
The advantage of saying something before it appears on screen is that it makes it look as though you're in charge, you know what's coming next and you're in control of slides that are merely supporting you (rather than being controlled or prompted by them). This is why my books and courses recommend that later rather than sooner is the safest guide to when you should press the button to bring on a new slide.
In this first sequence, Steve Jobs is going through the characteristics of note book computers before the super-thin MacBook Air that he's about to announce (here). But each of the bullet points appears before he makes the various points about them. Then, when he starts to allocate ticks and crosses to the list, the tick and crosses again come up on the screen before he pronounces verdicts on each one of them.
As you watch it, consider whether or not you think his performance would have improved if he'd waited to press the button later rather than sooner - and then compare it with what he does in the second clip.
2. Later rather than sooner
Shortly after the first sequence above, Jobs starts using the power of contrast to show how thin the MacBook Air is compared with the Sony TZ series notebook computers - and this time his timing is much better.
You'll see how the the green pictorial image of the MacBook Air appears just after he says "This is the MacBook Air" - prompting laughter, cheers and applause from the audience - after which he goes on to ram the contrast home with:
"The thickest part of the MacBook Air is still thinner than the thinnest part of the TZ series."