gjcope,
I'm unable to give you a measure of the latency between image capture and my perception of a rendered update; however, the delay between the ID_SEETHROUGH callback and when I Submit the texture to the compositor is typically at or under 11ms. The delay between callbacks is typically around 16ms, putting the callbacks at 60Hz.
I don't know enough about your application to assist; however, if you're using the C API, grab the Unreal or Unity Demo, and compare the results to your own to at least see if this is due to implementation. It sounds from that 21ms-33ms reference like your camera may not actually be running at the full 60Hz. Also worth verifying that any modification you're doing to the textures is done on your GPU, and that you're not juggling the texture between RAM and VRAM