I've been installing beta versions and testing capabilities.

In short, it goes like this.

Apple makes Leopard. Leopard is made with all sorts of new feature (many inside that people are unaware of). It is build with an architecture derived of large and clunky but solid structured code (Carbon). The parts of the system that are new are solidified an further tested.

Once Leopard is wide spread and tested, they completely re-write the structured code and replace the large clunky pieces with refined streamlined objects that can further be enhanced and extended in the future.

This new Object oriented codebase is called Snow-Leopard and although is very similar on the surface, is radically thinner and faster on the inside.

At this point Snow Leopard is the epitome of where OS X is developed to from an "under the hood" perspective. This will ultimately be the code base used for a long time.

Then Lion comes along... Truth be known, Lion is simple a package of enhancements which install atop Snow Leopard. In fact, you cannot even install Lion from scratch but must install Snow Leopard as a foundation first.

Then the enhancement "Lion" packaged is deployed on top.

In the world of UNIX, Lion is paper thin and nothing but fluff. However, in the world of quick apps and development, Lion opens doors for a huge amount of extensibility within and beyond Apple's dev teams.

Unfortunately though, all those enhancements do not increase the performance of the overall system, especially in areas that simply require raw processing such as with Catalyst.