I recently bought a Super-Takumar 50/1.4 and a Zuiko 28mm.
I enjoyed playing with these manual focus lenses once the adapters arrived. But my enthusiasm was tempered by the large amount of out of focus shots I was getting with my 5D. The ratio of good shots was disappointing. Yesterday I went for a walk with the 28mm and a Canon 20D and I was still not that happy.
After reading many pro and con reports on the merits of all kinds of focusing screen options I thought I would try the Canon 5D EsS screen. During my Pentax LX days I would swap screens all the time so this was a familiar procedure.
What a noticeable difference. I shot a bunch with the Tak wide open and voila: in focus images!
I will next try the 24-105/4 L as its my slowest lens. All my other glass is 2.8 or faster.
I wish I had tried this screen a long time ago.
Here is a quick test of our "hate posing for photos" cat indoors wide open at 1.4
Max