I think the beauty of OSX, at least for me, is that it's incredibly accessible for new comers but is still very deep for experienced users. I've only used OS X since 10.4 (had a mac as a kid on OS 9) but it seems like a regular occurance with using OS X is the "Oh! I can do that?" moment where you discover a new feature or a better way to improve your workflow. I'm sure all but the most seasoned of OS X users probably stumble across new features from time to time - things like Apple Scripts and Automator that aren't exactly major selling features and a lot of OS X users probably never touch, but those that do discover them usually benefit from it.
I think that Apple is great at pushing out features for "most" people and then a lot of advanced users focus on that aspect and overlook how deep the OS actually is. So with Lion, a lot of people seem to focus on the iPad-ification of the OS in terms of the look and even some of the functionality (full screen apps, launchpad, scrolling, etc) but forget that it still has a lot to offer for the more advanced user (and on top of that, a lot of the new features like the lights on the dock or the reverse scrolling can be turned off... at least in the dev previews).
As an example for Lion, the one thing that I'm excited for is the inclusion of Server features in to Lion because I would love to explore all of those tools. I'm sure I won't be the only one who experiments with VPNs or basic web hosting. I doubt that the "average" user is too concerned about that and I doubt that Apple will really spend a lot of time selling that as a feature but - like a lot of the other advanced features - just because Apple doesn't focus on them for their presentations or shine a spotlight on them on their website doesn't mean that the OS is all of a sudden becoming some ultra-basic, limited-use OS for the computer illiterate.