I'm working on the write up for this project at the moment. The best aspect of the language in my eyes is having a scriptable compiler with Haxe macros (macros themselves are also written in Haxe). In this project there's a macro that parses and extracts the variables from the shader glsl - so rather than the usual method for passing variables to shaders:

  gl.useProgram(program);
  mouseCoordLocation = gl.getUniformLocation(program, 'mouseCoord');

... then later during rendering ...

  gl.useProgram(program);
  gl.uniform2f(mouseCoordLocation, mouse.x, mouse.y);

With Haxe macros it becomes:

  program.mouseCoord = mouse;

Best of all it works with autocomplete! Checkout shaderblox by Sunjammer to try it for your self - it's quite experimental so in this project I'm using a fork with a few of the bugs patched https://github.com/haxiomic/shaderblox .It also supports fairly rudimentary shader inheritance which is terribly useful if you're not a fan of the rigidity of shader languages like glsl.

Alternatively, Ncannasse is working on a haxe-based shader langauge, hxsl which when ready will be my language of choice - not least because we'll be able to target glsl, AGAL and hlsl, maybe even Cg with a single codebase