The level 2 stuff (e.g.,
[email protected]~16 - 70A) tends to use a standard signalling method between the charging station and the charger in the car. So, for instance, the J1772 adapter that Tesla provides for Model S (or Roadster) to connect to public J1772 charging stations is just a physical pin to pin mechanical adapter so that the two can plug together.
DC "fast-charging" (or "quick-charging") isn't as simple. We know, at a minimum, that Tesla uses a different signalling method for the Model S to talk to the offboard charging equipment in their Supercharger. There will probably need to be some little "translation computer" in the adapter to go from something like Model S charge port to a CHAdeMO DC quick charger (like the Nissan LEAF uses.) I suspect that adapters for Model S to use a non-Tesla quick-charger will be quite a bit bigger and more expensive than their simple Level 2 J1772 adapter.
Tesla mentions that their Model S will use SuperChargers up to 90kW. Nissan LEAF CHAdeMO chargers are typically 50kW or less.
So, another difference is that Tesla's supercharger will offer slightly faster charging possibility that some of the alternatives.
But, at the end of the day, the Supercharger is "just another offboard DC charging system", so in that way it is similar to other DC quick chargers that have CHAdeMO or SAE combo plugs on them.
It is yet to be seen how the industry works out compatibility between systems. Will someone build a multi-charger with different plug types to suit different vehicles? Will Tesla build an adapter for Model S to use a CHAdeMO charger? Will someone build an adapter so a LEAF can charge at a Tesla supercharger? Plenty of unanswered questions here.