I'm blown away by just how responsive and fluid the UI was back then, most likely running on...what...a 33 MHz 68040 CPU? Sheesh. Consider that today the average CPU is probably at least 20-50x as fast just in clock speed (and many times faster with bus/bandwidth/etc. improvements), plus the very powerful hardware graphics acceleration we have today. Honestly, I don't notice much difference between what Steve demoed on that ancient machine and my dual G5 PowerMac, which is a bit depressing.
Secondly, where is the way-cool "DB Kit" that Steve demoed in the video? That would be so great to be able to use today, one has to wonder why it's not a part of the Cocoa APIs. I assume much of it is was split off to become WebObjects/EOF, but you can't even use that with Objective-C now, and since it's not integrated with Cocoa, developers generally can't/don't use it. That's a real shame, I believe there's a need for standard Cocoa database APIs, as well as a database that is installed by default in OS X, such as MySLQ, like Apache and JBoss are. Apple took most of the best parts of NeXTStep, but they missed a few good ideas too.