It does work though is a bit abrupt and can sometimes go way out of focus first. If your shooting something repeatable then it’s not too bad as you can have a second go at it
I have a Zacuto viewfinder loupe and I haven’t used it since I bought the GH2. I either use the electronic viewfinder or the lcd screen, usually flipped out. If you added the loupe then you can’t use the touch screen.