Intel Linux users as of today now have GL_ARB_copy_image support added to Mesa Git for the upcoming Mesa 10.3 release. ARB_copy_image as explained by the OpenGL registry comes down to, "[an] extension enables efficient image data transfer between image objects (i.e. textures and renderbuffers) without the need to bind the objects or otherwise configure the rendering pipeline. This is accomplised by adding a new entry-point CopyImageSubData, which takes a named source and destination."
GL_ARB_copy_image support is mandated by the OpenGL 4.3 specification. The i965 Intel driver's support for this extension is the first of the Mesa/Gallium3D drivers to support this extension (per this commit).