The gist is that they've created a better theory of flow separation (roughly speaking, where a flowing fluid "tears loose" from a boundary surface of some sort to make a sheet of fluid that folds up and projects out into the main flow).
Their theory deals only with incompressible flow, so I'm not sure how much this would help aerodynamic simulations, but it's probably got lots of applications in hydrodynamics and industrial process simulation.
This is one of the reasons why I get most of my news these days through HN, and typically read the comments first. I get a concise summary and usually more interesting links to the original research.
Typically, incompressible flow is valid in gases for Mach numbers less than 0.3, so this is relevant for automotive aerodynamics and wind turbines, but not for turboprops, jet engines, compressors, gas turbines, and most airplanes.
They've derived exact mathematical expressions for the shapes and locations of those flow separations, and it sounded like the whole derivation was based on the assumption of incompressibility, so I'm not sure how extensible their approach is to compressible flow.
That said, it's totally true that you could use this sort of code in gasdynamics situations where the compressibility doesn't matter much, as you pointed out.
The experimental setup they validated their code with used three liquids -- Fluorinert, glycerol, and vegetable oil -- shearing past each other and the walls of a container while being stirred slowly. All incompressible, true, but perhaps chosen for experimental convenience rather than any problem with their theory's handling of compressibility.
Their theory deals only with incompressible flow, so I'm not sure how much this would help aerodynamic simulations, but it's probably got lots of applications in hydrodynamics and industrial process simulation.
You can see the original papers at http://web.mit.edu/ghaller/www/papers.html.