When I first read your question, how long I have been using computers?  I didn't think it would be so dangerous, but as I considered it I suddenly realized that it has been a lot longer than I care to remember.  If you considered that I took Basic programming in college in 1980 it has been a very long time.  I am assuming that actually you are asking about personal computers, and in that case just for about 22 years.  My first computer was an Apple, but for the most part I have used the Windows OS.

The first interesting fact I found on the Mac OS was the Multi-touch Gestures.  I knew the function of using one finger, just like a mouse, but the uses of two and three fingers were new.  While this function does not have a lot of application on a desktop computer I can certainly see the value of know this with IPADs, at least I assume that it is the same with IPADs.

The next was about versions.  First of all with your help I was able to learn what they were and their application then I was learned about how to use them in the Lion OS system.  This seems to be a very valuable and useful tool for collaboration work.  It would be very helpful to view not only past work, but also who does what when several students are working together.

Finally learning what a Dock is and what the stacks are as well as how to manipulate the stacks was the third fact that I investigated.   I have used Mac enough to know that the icons were lined up along the bottom of the screen, but the truth is other than clicking on them that was all that I knew.  It would be helpful to be able to do more than this.