My Ec-S focus screen came today for my 1D MK IV. I popped it in, and my manual focusing did improve, but still not equal to AF or live view.
I played some more with hand held images from the 500mm mirror lens, but, for me, it was a exercise in frustration trying to setup a good exposure and then getting a sharp image. I ended up with only two of 20 or more that were presentable, and these were not all that sharp. I was using shutter speeds of 1/1500sec or more, so I had the ISO cranked up, even in very bright sunlight.
I gusee I'll list it on Craigslist or ebay, my vision is not up to it, and, my 100-400mmL blows it away. I can even crop my 100mm macro images and get better.