The current ES 2.0 standard says in corrolary 7: "The GL does not force left- or right-handedness on any of its coordinate systems"
What does this mean? An implementation can't help choosing left or right handed-ness. If that seems debatable, just make a tetrahedron with opaque faces and a blue peak pointing towards +ve z. Render it with no transforms at all but depth filtering, and either you see blue or you don't.
On my HTC Desire, I don't see blue, which (having used other colours to confirm that x is rightwards and y is towards the top of the screen) makes it a left handed coordinate system. This was a great surprise for me because all over the web it says that OpenGL is right handed.
So what's the deal with ES 2.0? Is this a bug in my phone or are they allowed to do this under the spec?
It would seem completely mad if every implementation was allowed to flip a coin over the handedness. That would make it impossible to write software that looked the same everywhere. But that corollary seems to mean just that.