I don't know if I would have figured out the really fun stuff if my son hadn't been able to point it out. For instance, I use an Airport Express for my wifi. I can play my iTunes music through the 1000-watt home entertainment system anywhere in the house. But Mountain Lion actually will play ANY computer sounds through Airport, so you can even play internet radio stations independent of iTunes. Like I said before, it's not groundbreaking, but it's a nice feature. Lots of other nice new stuff, too, but I'm not exactly blown away. Of course, I've already forgotten half of what he demonstrated to me.
And yes, it's cool that my son is a developer. It would have been even cooler if was a developer back when upgrades were $129.