I'm using NVIDIA's 310.90 drivers on a GeForce GT250. And I'm testing out ARB_internalformat_query2, to see what you get when you try different things.
One oddity is that basic image formats like GL_RGBA8 will, when queried with GL_READ_PIXELS, return GL_NO_SUPPORT. This means that it should not be possible to use glReadPixels on FBOs with such formats bound. This seems... unlikely. Especially as I tried it with texture targets GL_TEXTURE_2D and GL_RENDERBUFFER.
Because the operation is unsupported, I also got GL_NONE for GL_READ_PIXEL_FORMAT.
Also, I got GL_NONE for the TEXTURE_IMAGE_FORMAT and GET_TEXTURE_IMAGE_FORMAT. Oddly enough, the _TYPE versions return real values.