While OpenGL 3.0 is limited to if your graphics card can support it, but it can also be if your OS supports it.
Mac OS X Snow Leopard now only has support for OpenGL 2.0.
This will change soon though as an early build of Mac OS X 10.6.3 adds 95% support of OpenGL 3.0.
Almost supported. Image Credit: hardmac.com
This could open up more games for the Mac.
So while the new Macs support OpenGL 3.0 you will have to wait for 10.6.3 which is now in development.
I have written shaders in Cg and GLSL.
They’d better write a damn good implementation of that 5% that’s left or I’ll go hunt them with an axe.