<p>Since more than 30 years I at once changed to a plain matte screen, because split image and microprisms do bother me. Focusing was never a problem for me even with some AF-SLRs. Since I have a EF and a T90, I have no desire to change the screen, because split screen and microprisms are nearly not visible. I keep focusing via the matte part, because this way no recomposing is necessary. Especially with a fast lens, that is usualy used for portrait to blow out backround, it is very easy to focus.<br>
Grid screens I often used but not in terms of focusing.<br>
Recomposing is, as mentioned, indeed a problem for exposure, but light does normaly not change during a shooting. So use manuel exposure and stay with your measurement.</p>